Liquid-crystal medium

ABSTRACT

The present invention relates to a liquid crystal (LC) medium comprising a polymerizable compound, to a process for its preparation, to its use for optical, electro-optical and electronic purposes, in particular in LC displays, especially in an LC display of the polymer sustained alignment (PSA) type, and to an LC display, especially a PSA display, comprising it.

The present invention relates to a liquid crystal (LC) medium comprisinga polymerizable compound, to a process for its preparation, to its usefor optical, electro-optical and electronic purposes, in particular inLC displays, especially in an LC display of the polymer sustainedalignment (PSA) type, and to an LC display, especially a PSA display,comprising it.

BACKGROUND OF THE INVENTION

A liquid crystal display mode which has meanwhile found widespreadinterest and commercial use is the so-called PS (“polymer sustained”) orPSA (“polymer sustained alignment”) mode, for which the term “polymerstabilised” is also occasionally used. In PSA displays an LC medium isused that contains an LC mixture (hereinafter also referred to as “hostmixture”) and a small amount, typically <1% by weight, for example 0.2to 0.4% by weight, of one or more polymerizable compounds, preferablypolymerizable monomeric compounds. After filling the LC medium into thedisplay, the polymerizable compounds are polymerised or crosslinked insitu, usually by UV photopolymerization, optionally while a voltage isapplied to the electrodes of the display. The polymerisation is carriedout at a temperature where the LC medium exhibits a liquid crystalphase, usually at room temperature. The addition of polymerizablemesogenic or liquid-crystalline compounds, also known as reactivemesogens or “RMs”, to the LC host mixture has proven particularlysuitable.

The PS(A) mode is meanwhile used in various conventional LC displaytypes. Thus, for example, PS-VA (“vertically aligned”), PS-OCB(“optically compensated bend”), PS-IPS (“in-plane switching”), PS-FFS(“fringe-field switching”), PS-UB-FFS (“Ultra Brightness FFS) and PS-TN(“twisted nematic”) displays are known. The polymerization of the RMspreferably takes place with an applied voltage in the case of PS-VA andPS-OCB displays, and with or without, preferably without, an appliedvoltage in the case of PS-IPS displays. As a result a pretilt angle ofthe LC molecules is generated in the display cell. In case of PS-OCBdisplays, for example, it is possible for the bend structure to bestabilized so that an offset voltage is unnecessary or can be reduced.In case of PS-VA displays, the pretilt has a positive effect on theresponse times. For PS-VA displays, a standard MVA (“multidomain VA”) orPVA (“patterned VA”) pixel and electrode layout can be used. It is alsopossible to use only one structured electrode without protrusions, whichsignificantly simplifies production and improves contrast andtransparency.

Furthermore, the so-called posi-VA mode (“positive VA”) has proven to beparticularly suitable. Like in conventional VA and PS-VA displays, theinitial orientation of the LC molecules in posi-VA displays ishomeotropic, i.e. substantially perpendicular to the substrates, in theinitial state when no voltage is applied. However, in contrast toconventional VA and PS-VA displays, in posi-VA displays LC media withpositive dielectric anisotropy are used. Like in IPS and PS-IPSdisplays, the two electrodes in posi-VA displays are arranged only onone of the two substrates, and preferably exhibit intermeshed,comb-shaped (interdigital) structures. Upon application of a voltage tothe interdigital electrodes, which create an electrical field that issubstantially parallel to the layer of the LC medium, the LC moleculesare switched to an orientation substantially parallel to the substrates.In posi-VA displays, a polymer stabilization by addition of RMs to theLC medium, which are then polymerized in the display, has also proven tobe advantageous.

Thereby a significant reduction of the switching times can be achieved.

PS-VA displays are described for example in EP1170626 A2, U.S. Pat. No.6,861,107, U.S. Pat. No. 7,169,449, US2004/0191428A1, US2006/0066793A1and US2006/0103804A1. PS-OCB displays are described for example inT.-J-Chen et al., Jpn. J. Appl. Phys. 45, 2006, 2702-2704 and S. H. Kim,L.-C-Chien, Jpn. J. Appl. Phys. 43, 2004, 7643-7647. PS-IPS displays aredescribed for example in U.S. Pat. No. 6,177,972 and Appl. Phys. Lett.1999, 75(21), 3264. PS-TN displays are described for example in OpticsExpress 2004, 12(7), 1221.

PSA displays can be operated as either active-matrix or passive-matrixdisplays. In case of active-matrix displays individual pixels areusually addressed by integrated, non-linear active elements like forexample transistors (such as thin-film transistors or “TFTs”), whereasin passive-matrix displays individual pixels are usually addressed bythe multiplex method as known from prior art.

A PSA display may also comprise an alignment layer on one or both of thesubstrates forming the display cell. The alignment layer is usuallyapplied on the electrodes (in case such electrodes are present) suchthat it is in contact with the LC medium and induces initial alignmentof the LC molecules. The alignment layer may comprise or consist of, forexample, a polyimide, which may also be rubbed or prepared by aphotoalignment method.

In particular for monitor and especially TV applications optimization ofthe response times, but also of the contrast and luminance (and thustransmission) of the LC display is still desired. The PSA method canprovide significant advantages here. Especially in case of PS-VA,PS-IPS, PS-FFS and PS-posi-VA displays, a shortening of the responsetimes, which correlate with a measurable pretilt in test cells, can beachieved without significant adverse effects on other parameters.

Prior art has suggested biphenyl diacrylates or dimethacrylates, whichare optionally fluorinated, as RMs for use in PSA displays

However, the problem arises that not all combinations of LC host mixtureand RM(s) are suitable for use in PSA displays because, for example,only inadequate tilt angles or no tilt angles at all could be generatedor because, for example, the voltage holding ratio (VHR) is inadequatefor TFT display applications. In addition, it has been found that the LCmixtures and RMs known from prior art still have some disadvantages whenused in PSA displays. Thus, not every known RM which is soluble in theLC host mixture is suitable for use in PSA displays. In addition, it isoften difficult to find a suitable selection criterion for the RMbesides direct measurement of the pretilt in the PSA display. The choiceof suitable RMs becomes even smaller if UV photopolymerization withoutthe addition of photoinitiators is desired, which is advantageous forcertain applications.

In addition, the selected combination of LC host mixture/RM should havea low rotational viscosity and good electrical properties, in particulara high VHR. In PSA displays, a high VHR after irradiation with UV lightis particularly important, because UV exposure does not only occur asnormal exposure during operation of the finished display, but is also anecessary part of the display production process.

In particular, it is desirable to have available improved materials forPSA displays which produce a particularly small pretilt angle. Preferredmaterials are those which, compared to prior art materials, can generatea lower pretilt angle after the same exposure time, and/or can generateat least the same pretilt angle after a shorter exposure time. Thiswould allow to reduce the display production time (“tact time”) andproduction costs.

A further problem in the production of PSA displays is the presence andremoval of residual amounts of unpolymerized RMs after thepolymerisation step that is necessary for generation of the pretiltangle in the display.

Unreacted RMs may adversely affect the properties of the display, forexample by polymerizing in an uncontrolled manner during displayoperation.

Thus, the PSA displays known from prior art often exhibit the undesiredeffect of so-called “image sticking” or “image burn”, i.e. the imageproduced in the LC display by temporary addressing of individual pixelsstill remains visible even after the electric field in these pixels hasbeen switched off, or after other pixels have been addressed.

Image sticking can occur for example if LC host mixtures having a lowVHR are used. The UV component of daylight or the display backlight cancause undesired decomposition reactions of the LC molecules and initiatethe production of ionic or free-radical impurities. These can accumulatein particular at the electrodes or the alignment layers, where theyreduce the effective applied voltage. This effect can also be observedin conventional LC displays without a polymer component.

An additional image sticking effect caused by the presence ofunpolymerized RMs is often observed in PSA displays. Uncontrolledpolymerization of the residual RMs is initiated by UV light from theenvironment or the backlight. In the switched display areas, thischanges the tilt angle after a number of addressing cycles. As a result,a change in transmission in the switched areas may occur, while itremains unchanged in the unswitched areas.

During production of the PSA display it is therefore desirable thatpolymerization of the RMs proceeds as completely as possible and thepresence of unpolymerized RMs in the display can be excluded or reducedto a minimum. Thus, RMs and LC host mixtures are required which enableor support quick and complete polymerization of the RMs. In addition, acontrolled reaction of the residual RM amounts is desirable. This couldbe achieved by providing improved RMs that polymerize quicker and moreeffectively than the RMs of prior art.

A further problem that has been observed in the operation of PSAdisplays is the stability of the pretilt angle. Thus, it was observedthat the pretilt angle, which is generated during display manufacture bypolymerizing the RMs, does not remain constant but can deteriorate afterthe display was subjected to voltage stress during display operation.This can negatively affect the display performance, e.g. by increasingthe black state transmission and hence lowering the contrast.

Another problem to be solved is that the RMs of prior art do often havehigh melting points, and do only show limited solubility in manycommonly used LC mixtures. As a result the RMs tend to spontaneouslycrystallise out of the LC mixture. In addition, the risk of spontaneouspolymerization prevents that the LC host mixture can be warmed in orderto better dissolve the RMs, so that a high solubility even at roomtemperature is required. In addition, there is a risk of phaseseparation, for example when filling the LC medium into the LC display(chromatography effect), which may greatly impair the homogeneity of thedisplay. This is further aggravated by the fact that the LC media areusually filled in the display at low temperatures in order to reduce therisk of spontaneous polymerization (see above), which in turn has anadverse effect on the solubility.

Another problem observed in prior art is that the use of conventional LCmedia in LC displays, including but not limited to displays of the PSAtype, often leads to the occurrence of mura in the display, especiallywhen the LC medium is filled in the display by using the one dropfilling (ODF) method. This phenomenon is also known as “ODF mura”. It istherefore desirable to provide LC media which lead to reduced ODF mura.

Another problem observed in prior art is that LC media for use in PSAdisplays, including but not limited to displays of the PSA type, dooften exhibit high viscosities and, as a consequence, high switchingtimes. In order to reduce the viscosity and response time of the LCmedium, it has been suggested in prior art to add LC compounds with analkenyl group. However, it was observed that LC media containing alkenylcompounds often show a decrease of the reliability and stability, and adecrease of the VHR especially after exposure to UV radiation.Especially for use in PSA displays this is a considerable disadvantage,because the photo-polymerization of the RMs in the PSA display isusually carried out by exposure to UV radiation, which may cause a VHRdrop in the LC medium.

In prior art LC media for use in PSA displays have been proposed whereinthe LC host mixture contains one or more terphenyl compounds in order toenhance polymerization of the RMs. However, the addition of terphenylcompounds increases the viscosity of the LC host mixture, thus leadingto slower response times. Besides the addition of terphenyl compoundscan lead to reduced reliability and a drop of the VHR after UV stress inthe LC medium.

It is therefore another problem to provide LC mixtures and LC media forPSA displays which show a reduced viscosity and a high VHR, while at thesame time enabling quick and complete polymerization of the RMs.

There is thus still a great demand for PSA displays and LC media andpolymerizable compounds for use in such displays, which do not show thedrawbacks as described above, or only do so to a small extent, and haveimproved properties.

In particular, there is a great demand for PSA displays, and LC mixturesand RMs for use in such PSA displays, which enable a high specificresistance at the same time as a large working-temperature range, shortresponse times, even at low temperatures, a low threshold voltage, a lowpretilt angle, a multiplicity of grey shades, high contrast and a broadviewing angle, high reliability and high values of the VHR after UVexposure, and, in case of the RMs, have low melting points and a highsolubility in the LC host mixture. In PSA displays for mobileapplications, it is especially desired to have available LC media thatshow low threshold voltage and high birefringence.

The invention is based on the object of providing novel suitablematerials, in particular RMs, LC host mixtures, and LC media comprisingthe same, for use in PSA displays, which do not have the disadvantagesindicated above or do so to a reduced extent.

In particular, the invention is based on the object of providing LCmedia for use in PSA displays, which enable very high specificresistance values, high VHR values, high reliability, low thresholdvoltages, short response times, high birefringence, show good UVabsorption especially at longer wavelengths, allow quick and completepolymerization of the RMs contained therein, allow the generation of alow pretilt angle as quickly as possible, enable a high stability of thepretilt even after longer time and/or after UV exposure, reduce orprevent the occurrence of image sticking in the display, and reduce orprevent the occurrence of ODF mura in the display.

Another object of the invention is to solve the problem of providing LCmixtures and LC media for PSA displays which show a reduced viscosityand a high VHR while enabling quick and complete polymerization of theRMs.

The above objects have been achieved in accordance with the presentinvention by materials and processes as described and claimed in thepresent application.

It has surprisingly been found that at least some of the above-mentionedproblems can be solved by using an LC medium comprising a polymerizablecomponent and an LC host mixture containing compounds of formula B and Qas disclosed and claimed hereinafter.

Thus it was found that, when using an LC medium as disclosed and claimedhereinafter in PSA displays, it is possible to lower the viscosity ofthe LC host mixture while still maintaining high VHR, high UV absorptionwhich is needed for quick and complete polymerization, and a strong tiltangle generation.

In particular, it was found that an improvement of the viscosity can beachieved by adding a compound of formula B to the LC medium, and animprovement of the VHR can be achieved by adding a compound of formula Qto the LC medium.

The use of LC media according to the present invention facilitates aquick and complete UV-photo-polymerization reaction in particular at lowUV energy and/or longer UV wavelengths in the range from 300-380 nm andespecially above 340 nm, which are considerable advantages for thedisplay manufacturing process. Besides, the use of LC media according tothe present invention allows a fast generation of large and stablepretilt angles, reduces image sticking and ODF mura in the display,leads to a high VHR value after UV photo-polymerization, and enables toachieve fast response times, a low threshold voltage and a highbirefringence.

SUMMARY OF THE INVENTION

The invention relates to a liquid crystal (LC) medium comprising one ormore polymerizable compounds, one or more compounds of formula B, andone or more compounds of formula Q

in which the individual radicals, on each occurrence identically ordifferently, and each, independently of one another, have the followingmeaning:

-   R¹, R², R^(Q) alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C    atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which    are optionally fluorinated,-   X^(Q) F, Cl, halogenated alkyl or alkoxy having 1 to 6 C atoms or    halogenated alkenyl or alkenyloxy having 2 to 6 C atoms,-   L¹, L² F or Cl, preferably F,-   L^(Q1)-L^(Q6) H, F or Cl, preferably H or F, with at least one of    L^(Q1) to L^(Q6) being F or Cl, preferably F.

The invention further relates to a liquid crystal (LC) medium comprising

-   -   a polymerizable component A) comprising, preferably consisting        of, one or more polymerizable compounds, and    -   a liquid-crystalline component B), hereinafter also referred to        as “LC host mixture”, comprising, preferably consisting of, one        or more mesogenic or liquid-crystalline compounds,

wherein component B) comprises one or more compounds of formula B andone or more compounds of formula Q as defined above and below.

The liquid-crystalline component B) of an LC medium according to thepresent invention is hereinafter also referred to as “LC host mixture”,and preferably contains only LC compounds that are selected fromlow-molecular-weight compounds which are unpolymerizable, like those offormula B and Q, and optionally contains additives like polymerizationinitiators, inhibitors etc.

The invention furthermore relates to an LC medium or LC display asdescribed above and below, wherein the polymerizable compounds ofcomponent A) are polymerized.

The invention furthermore relates to a process for preparing an LCmedium as described above and below, comprising the steps of mixing oneor more compounds of formula B and one or more compounds of formula Q,or an LC host mixture or LC component B) as described above and below,with one or more polymerizable compounds, and optionally with further LCcompounds and/or additives.

The invention further relates to the use of LC medium in LC displays,especially in PSA displays.

The invention furthermore relates to the use of LC medium according tothe invention in PSA displays, in particular the use in PSA displayscontaining an LC medium, for the production of a tilt angle in the LCmedium by in-situ polymerization of the polymerizable compound(s) ofcomponent B) in the PSA display, preferably in an electric or magneticfield.

The invention furthermore relates to an LC display comprising one ormore compounds of formula I or an LC medium according to the invention,which is preferably a PSA display, very preferably a PS-VA, PS-IPS orPS-UB-FFS display.

The invention furthermore relates to an LC display comprising a polymerobtainable by polymerization of one or more compounds of formula I or ofa polymerizable component A) as described above, or comprising an LCmedium according to the invention, which is preferably a PSA display,very preferably a PS-VA, PS-IPS or PS-UB-FFS display

The invention furthermore relates to an LC display of the PSA typecomprising two substrates, at least one which is transparent to light,an electrode provided on each substrate or two electrodes provided ononly one of the substrates, and located between the substrates a layerof an LC medium that comprises one or more polymerizable compounds andan LC component as described above and below, wherein the polymerizablecompounds are polymerized between the substrates of the display.

The invention furthermore relates to a process for manufacturing an LCdisplay as described above and below, comprising the steps of filling orotherwise providing an LC medium, which comprises one or morepolymerizable compounds as described above and below, between thesubstrates of the display, and polymerizing the polymerizable compounds.

The PSA displays according to the invention have two electrodes,preferably in the form of transparent layers, which are applied to oneor both of the substrates. In some displays, for example in PS-VAdisplays, one electrode is applied to each of the two substrates. Inother displays, for example in PS-IPS or PS-UB-FFS displays, bothelectrodes are applied to only one of the two substrates.

In a preferred embodiment the polymerizable component is polymerized inthe LC display while a voltage is applied to the electrodes of thedisplay.

The polymerizable compounds of the polymerizable component arepreferably polymerised by photo-polymerization, very preferably by UVphoto-polymerization.

DETAILED DESCRIPTION OF THE INVENTION

Unless stated otherwise, the polymerizable compounds are preferablyselected from achiral compounds.

As used herein, the terms “active layer” and “switchable layer” mean alayer in an electrooptical display, for example an LC display, thatcomprises one or more molecules having structural and opticalanisotropy, like for example LC molecules, which change theirorientation upon an external stimulus like an electric or magneticfield, resulting in a change of the transmission of the layer forpolarized or unpolarized light.

As used herein, the terms “tilt” and “tilt angle” will be understood tomean a tilted alignment of the LC molecules of an LC medium relative tothe surfaces of the cell in an LC display (here preferably a PSAdisplay). The tilt angle here denotes the average angle (<90°) betweenthe longitudinal molecular axes of the LC molecules (LC director) andthe surface of the plane-parallel outer plates which form the LC cell. Alow value for the tilt angle (i.e. a large deviation from the 90° angle)corresponds to a large tilt here. A suitable method for measurement ofthe tilt angle is given in the examples. Unless indicated otherwise,tilt angle values disclosed above and below relate to this measurementmethod.

As used herein, the terms “reactive mesogen” and “RM” will be understoodto mean a compound containing a mesogenic or liquid crystallineskeleton, and one or more functional groups attached thereto which aresuitable for polymerization and are also referred to as “polymerizablegroup” or “P”.

Unless stated otherwise, the term “ polymerizable compound” as usedherein will be understood to mean a polymerizable monomeric compound.

As used herein, the term “low-molecular-weight compound” will beunderstood to mean to a compound that is monomeric and/or is notprepared by a polymerization reaction, as opposed to a “polymericcompound” or a “polymer”.

As used herein, the term “ unpolymerizable compound” will be understoodto mean a compound that does not contain a functional group that issuitable for polymerization under the conditions usually applied for thepolymerisation of the RMs.

The term “mesogenic group” as used herein is known to the person skilledin the art and described in the literature, and means a group which, dueto the anisotropy of its attracting and repelling interactions,essentially contributes to causing a liquid-crystal (LC) phase inlow-molecular-weight or polymeric substances. Compounds containingmesogenic groups (mesogenic compounds) do not necessarily have to havean LC phase themselves. It is also possible for mesogenic compounds toexhibit LC phase behavior only after mixing with other compounds and/orafter polymerization. Typical mesogenic groups are, for example, rigidrod- or disc-shaped units. An overview of the terms and definitions usedin connection with mesogenic or LC compounds is given in Pure Appl.Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew.Chem. 2004, 116, 6340-6368.

The term “spacer group”, hereinafter also referred to as “Sp”, as usedherein is known to the person skilled in the art and is described in theliterature, see, for example, Pure Appl. Chem. 2001, 73(5), 888 and C.Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368. Asused herein, the terms “spacer group” or “spacer” mean a flexible group,for example an alkylene group, which connects the mesogenic group andthe polymerizable group(s) in a polymerizable mesogenic compound.

Above and below,

denote a trans-1,4-cyclohexylene ring, and

denote a 1,4-phenylene ring.

Above and below “organic group” denotes a carbon or hydrocarbon group.

“Carbon group” denotes a mono- or polyvalent organic group containing atleast one carbon atom, where this either contains no further atoms (suchas, for example, —C≡C—) or optionally contains one or more furtheratoms, such as, for example, N, O, S, B, P, Si, Se, As, Te or Ge (forexample carbonyl, etc.). The term “hydrocarbon group” denotes a carbongroup which additionally contains one or more H atoms and optionally oneor more heteroatoms, such as, for example, N, O, S, B, P, Si, Se, As, Teor Ge.

“Halogen” denotes F, Cl, Br or I.

—CO—, —C(═O)— and —C(O)— denote a carbonyl group, i.e.

A carbon or hydrocarbon group can be a saturated or unsaturated group.Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups. Acarbon or hydrocarbon radical having more than 3 C atoms can bestraight-chain, branched and/or cyclic and may also contain spiro linksor condensed rings.

The terms “alkyl”, “aryl”, “heteroaryl”, etc., also encompass polyvalentgroups, for example alkylene, arylene, heteroarylene, etc.

The term “aryl” denotes an aromatic carbon group or a group derivedtherefrom. The term “heteroaryl” denotes “aryl” as defined above,containing one or more heteroatoms, preferably selected from N, O, S,Se, Te, Si and Ge.

Preferred carbon and hydrocarbon groups are optionally substituted,straight-chain, branched or cyclic, alkyl, alkenyl, alkynyl, alkoxy,alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxyhaving 1 to 40, preferably 1 to 20, very preferably 1 to 12, C atoms,optionally substituted aryl or aryloxy having 5 to 30, preferably 6 to25, C atoms, or optionally substituted alkylaryl, arylalkyl,alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl,arylcarbonyloxy and aryloxycarbonyloxy having 5 to 30, preferably 6 to25, C atoms, wherein one or more C atoms may also be replaced by heteroatoms, preferably selected from N, O, S, Se, Te, Si and Ge.

Further preferred carbon and hydrocarbon groups are C₁-C₂₀ alkyl, C₂-C₂₀alkenyl, C₂-C₂₀ alkynyl, C₃-C₂₀ allyl, C₄-C₂₀ alkyldienyl, C₄-C₂₀polyenyl, C₆-C₂₀ cycloalkyl, C₄-C₁₅ cycloalkenyl, C₆-C₃₀ aryl, C₆-C₃₀alkylaryl, C₆-C₃₀ arylalkyl, C₆-C₃₀ alkylaryloxy, C₆-C₃₀ arylalkyloxy,C₂-C₃₀ heteroaryl, C₂-C₃₀ heteroaryloxy.

Particular preference is given to C₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂alkynyl, C₆-C₂₅ aryl and C₂-C₂₅ heteroaryl.

Further preferred carbon and hydrocarbon groups are straight-chain,branched or cyclic alkyl having 1 to 20, preferably 1 to 12, C atoms,which are unsubstituted or mono- or polysubstituted by F, Cl, Br, I orCN and in which one or more non-adjacent CH₂ groups may each bereplaced, independently of one another, by —C(R^(x))═C(R^(x))—, —C≡C—,—N(R^(x))—, —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a way thatO and/or S atoms are not linked directly to one another.

R^(x) preferably denotes H, F, Cl, CN, a straight-chain, branched orcyclic alkyl chain having 1 to 25 C atoms, in which, in addition, one ormore non-adjacent C atoms may be replaced by —O—, —S—, —CO—, —CO—O—,—O—CO—, —O—CO—O— and in which one or more H atoms may be replaced by For Cl, or denotes an optionally substituted aryl or aryloxy group with 6to 30 C atoms, or an optionally substituted heteroaryl or heteroaryloxygroup with 2 to 30 C atoms.

Preferred alkyl groups are, for example, methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl,s-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl,cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl,n-dodecyl, dodecanyl, trifluoromethyl, perfluoro-n-butyl,2,2,2-trifluoroethyl, perfluorooctyl, perfluorohexyl, etc.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl,pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl,octenyl, cyclooctenyl, etc.

Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl,pentynyl, hexynyl, octynyl, etc.

Preferred alkoxy groups are, for example, methoxy, ethoxy,2-methoxy-ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy,t-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy,n-nonoxy, n-decoxy, n-undecoxy, n-dodecoxy, etc.

Preferred amino groups are, for example, dimethylamino, methylamino,methylphenylamino, phenylamino, etc.

Aryl and heteroaryl groups can be monocyclic or polycyclic, i.e. theycan contain one ring (such as, for example, phenyl) or two or morerings, which may also be fused (such as, for example, naphthyl) orcovalently bonded (such as, for example, biphenyl), or contain acombination of fused and linked rings. Heteroaryl groups contain one ormore heteroatoms, preferably selected from O, N, S and Se.

Particular preference is given to mono-, bi- or tricyclic aryl groupshaving 6 to 25 C atoms and mono-, bi- or tricyclic heteroaryl groupshaving 5 to 25 ring atoms, which optionally contain fused rings and areoptionally substituted. Preference is furthermore given to 5-, 6- or7-membered aryl and heteroaryl groups, in which, in addition, one ormore CH groups may be replaced by N, S or O in such a way that O atomsand/or S atoms are not linked directly to one another.

Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl,[1,1′:3′,1″]terphenyl-2′-yl, naphthyl, anthracene, binaphthyl,phenanthrene, 9,10-dihydro-phenanthrene, pyrene, dihydropyrene,chrysene, perylene, tetracene, pentacene, benzopyrene, fluorene, indene,indenofluorene, spirobifluorene, etc.

Preferred heteroaryl groups are, for example, 5-membered rings, such aspyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole,furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole,1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole,1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole,1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings, such aspyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine,1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine,1,2,3,5-tetrazine, or condensed groups, such as indole, isoindole,indolizine, indazole, benzimidazole, benzotriazole, purine,naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole,quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole,phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran,dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline,benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine,phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine,quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline,phenanthridine, phenanthroline, thieno[2,3b]thiophene,thieno[3,2b]thiophene, dithienothiophene, isobenzothiophene,dibenzothiophene, benzothiadiazothiophene, or combinations of thesegroups.

The aryl and heteroaryl groups mentioned above and below may also besubstituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl orfurther aryl or heteroaryl groups.

The (non-aromatic) alicyclic and heterocyclic groups encompass bothsaturated rings, i.e. those containing exclusively single bonds, andalso partially unsaturated rings, i.e. those which may also containmultiple bonds.

Heterocyclic rings contain one or more heteroatoms, preferably selectedfrom Si, O, N, S and Se.

The (non-aromatic) alicyclic and heterocyclic groups can be monocyclic,i.e. contain only one ring (such as, for example, cyclohexane), orpolycyclic, i.e. contain a plurality of rings (such as, for example,decahydronaphthalene or bicyclooctane). Particular preference is givento saturated groups. Preference is furthermore given to mono-, bi- ortricyclic groups having 5 to 25 ring atoms, which optionally containfused rings and are optionally substituted. Preference is furthermoregiven to 5-, 6-, 7- or 8-membered carbocyclic groups, in which, inaddition, one or more C atoms may be replaced by Si and/or one or moreCH groups may be replaced by N and/or one or more non-adjacent CH₂groups may be replaced by —O— and/or —S—.

Preferred alicyclic and heterocyclic groups are, for example, 5-memberedgroups, such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran,pyrrolidine, 6-membered groups, such as cyclohexane, silinane,cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane,1,3-dithiane, piperidine, 7-membered groups, such as cycloheptane, andfused groups, such as tetrahydronaphthalene, decahydronaphthalene,indane, bicyclo[1.1.1]-pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl,spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl.

Preferred substituents are, for example, solubility-promoting groups,such as alkyl or alkoxy, electron-withdrawing groups, such as fluorine,nitro or nitrile, or substituents for increasing the glass transitiontemperature (Tg) in the polymer, in particular bulky groups, such as,for example, t-butyl or optionally substituted aryl groups.

Preferred substituents, hereinafter also referred to as “L”, are F, Cl,Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN, —C(═O)N(R^(x))₂, —C(═O)Y¹,—C(═O)R^(x), —N(R^(x))₂, straight-chain or branched alkyl, alkoxy,alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxyeach having 1 to 25 C atoms, in which one or more H atoms may optionallybe replaced by F or Cl, optionally substituted silyl having 1 to 20 Siatoms, or optionally substituted aryl having 6 to 25, preferably 6 to15, C atoms,

wherein R^(x) denotes H, F, Cl, CN, or straight chain, branched orcyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacentCH₂-groups are optionally replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—,—O—CO—O— in such a manner that O— and/or S-atoms are not directlyconnected with each other, and wherein one or more H atoms are eachoptionally replaced by F, Cl, P— or P-Sp-, and

Y¹ denotes halogen.

“Substituted silyl or aryl” preferably means substituted by halogen,—CN, R⁰, —OR⁰, —CO—R⁰, —CO—O—R⁰, —O—CO—R⁰ or —O—CO—O—R⁰, wherein R⁰denotes H or alkyl with 1 to 20 C atoms.

Particularly preferred substituents L are, for example, F, Cl, CN, NO₂,CH₃, C₂H₅, OCH₃, OC₂H₅, COCH₃, COC₂H₅, COOCH₃, COOC₂H₅, CF₃, OCF₃,OCHF₂, OC₂F₅, furthermore phenyl.

is preferably

in which L has one of the meanings indicated above.

The polymerizable group P is a group which is suitable for apolymerization reaction, such as, for example, free-radical or ionicchain polymerisation, polyaddition or polycondensation, or for apolymer-analogous reaction, for example addition or condensation onto amain polymer chain. Particular preference is given to groups for chainpolymerization, in particular those containing a C═C double bond or—C≡C— triple bond, and groups which are suitable for polymerization withring opening, such as, for example, oxetane or epoxide groups.

Preferred groups P are selected from the group consisting ofCH₂═CW¹—CO—O—, CH₂═CW¹—CO—,

CH₂═CW²—(O)_(k3)—, CW¹═CH—CO—(O)_(k3)—, CW¹═CH—CO—NH—, CH₂═CW¹—CO—NH—,CH₃—CH═CH—O—, (CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—, (CH₂═CH)₂CH—O—,(CH₂═CH—CH₂)₂N—, (CH₂═CH—CH₂)₂N—CO—, HO—CW²W³—, HS—CW²W³—, HW²N—,HO—CW²W³—NH—, CH₂═CW¹—CO—NH—, CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—,CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—, Phe-CH═CH—, HOOC—, OCN— and W⁴W⁵W⁶Si—,in which W¹ denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 Catoms, in particular H, F, Cl or CH₃, W² and W³ each, independently ofone another, denote H or alkyl having 1 to 5 C atoms, in particular H,methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of oneanother, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms,W⁷ and W⁸ each, independently of one another, denote H, Cl or alkylhaving 1 to 5 C atoms, Phe denotes 1,4-phenylene, which is optionallysubstituted by one or more radicals L as defined above which are otherthan P-Sp-, k₁, k₂ and k₃ each, independently of one another, denote 0or 1, k₃ preferably denotes 1, and k₄ denotes an integer from 1 to 10.

Very preferred groups P are selected from the group consisting ofCH₂═CW¹—CO—O—, CH₂═CW¹—CO—,

CH₂═CW²—O—, CH₂═CW²—, CW¹═CH—CO—(O)_(k3)—, CW¹═CH—CO—NH—,CH₂═CW¹—CO—NH—, (CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—, (CH₂═CH)₂CH—O—,(CH₂═CH—CH₂)₂N—, (CH₂═CH—CH₂)₂N—CO—, CH₂═CW¹—CO—NH—,CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—, CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—,Phe-CH═CH— and W⁴W⁵W⁶Si—, in which W¹ denotes H, F, Cl, CN, CF₃, phenylor alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH₃, W² and W³each, independently of one another, denote H or alkyl having 1 to 5 Catoms, in particular H, methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each,independently of one another, denote Cl, oxaalkyl or oxacarbonylalkylhaving 1 to 5 C atoms, W⁷ and W⁸ each, independently of one another,denote H, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene,k₁, k₂ and k₃ each, independently of one another, denote 0 or 1, k₃preferably denotes 1, and k₄ denotes an integer from 1 to 10.

Very particularly preferred groups P are selected from the groupconsisting of CH₂═CW¹—CO—O—, in particular CH₂═CH—CO—O—,CH₂═C(CH₃)—CO—O— and CH₂═CF—CO—O—, furthermore CH₂═CH—O—,(CH₂═CH)₂CH—O—CO—, (CH₂═CH)₂CH—O—,

Further preferred polymerizable groups P are selected from the groupconsisting of vinyloxy, acrylate, methacrylate, fluoroacrylate,chloroacrylate, oxetane and epoxide, most preferably from acrylate andmethacrylate.

If Sp is different from a single bond, it is preferably of the formulaSp″-X″, so that the respective radical P-Sp- conforms to the formulaP-Sp″-X″—, wherein

-   Sp″ denotes alkylene having 1 to 20, preferably 1 to 12, C atoms,    which is optionally mono- or polysubstituted by F, Cl, Br, I or CN    and in which, in addition, one or more non-adjacent CH₂ groups may    each be replaced, independently of one another, by —O—, —S—, —NH—,    —N(R⁰)—, —Si(R⁰R⁰⁰)—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —S—CO—,    —CO—S—, —N(R⁰⁰)—CO—O—, —O—CO—N(R⁰)—, —N(R⁰)—CO—N(R⁰⁰)—, —CH═CH— or    —C≡C— in such a way that O and/or S atoms are not linked directly to    one another,-   X″ denotes —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CO—N(R⁰)—,    —N(R⁰)—CO—, —N(R⁰)—CO—N(R⁰⁰)—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—,    —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—,    —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—, —CY²═CY³—, —C≡C—, —CH═CH—CO—O—,    —O—CO—CH═CH— or a single bond,-   R⁰ and R⁰⁰ each, independently of one another, denote H or alkyl    having 1 to 20 C atoms, and-   Y² and Y³ each, independently of one another, denote H, F, Cl or CN.-   X″ is preferably —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NR⁰—,    —NR⁰—CO—, —NR⁰—CO—NR⁰⁰— or a single bond.

Typical spacer groups Sp and -Sp″-X″— are, for example, —(CH₂)_(p1)—,—(CH₂CH₂O)_(q1)—CH₂CH₂—, —CH₂CH₂—S—CH₂CH₂—, —CH₂CH₂—NH—CH₂CH₂— or—(SiR⁰R⁰⁰—O)_(p1)—, in which p1 is an integer from 1 to 12, q1 is aninteger from 1 to 3, and R⁰ and R⁰⁰ have the meanings indicated above.

Particularly preferred groups Sp and -Sp″-X″— are —(CH₂)_(p1)—,—(CH₂)_(p1)—O—, —(CH₂)_(p1)—O—CO—, —(CH₂)_(p1)—CO—O—, and—(CH₂)_(p1)—O—CO—O—, in which p1 and q1 have the meanings indicatedabove.

Particularly preferred groups Sp″ are, in each case straight-chain,ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene,nonylene, decylene, undecylene, dodecylene, octadecylene,ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene,ethylene-N-methyliminoethylene, 1-methylalkylene, ethenylene,propenylene and butenylene.

The compounds of formula B are preferably selected of formula B1

wherein alkyl denotes a straight-chain alkyl radical having 1-6 C atoms,and (O) denotes an oxygen atom or a single bond. Very preferred arecompounds of formula B1 wherein both groups (O) denote an oxygen atomand alkyl is methyl, ethyl, propyl, butyl, pentyl or hexyl, which arepreferably straight-chained.

Preferably the proportion of compounds of formula B or B1 in the LCmedium, preferably in component B) of the LC medium, is from 0.5 to 20%,very preferably from 1 to 15%, most preferably from 1 to 10%.

In another preferred embodiment of the present invention the proportionof compounds of formula B or B1 in the LC medium, preferably incomponent B) of the LC medium, is ≧3%, more preferably ≧4%. In anotherpreferred embodiment of the present invention the proportion ofcompounds of formula B or B1 in the LC medium, preferably in componentB) of the LC medium, is ≦20%, more preferably ≦15%. Very preferably theproportion of compounds of formula B or B1 in the LC medium, preferablyin component B) of the LC medium, is from 3 to 20%, most preferably from4 to 15%.

Preferably the LC medium contains 1 to 5, preferably 1, 2 or 3 compoundsof formula B or B1.

Preferred compounds of formula Q, Q1 and Q2 are those wherein L^(Q3) andL^(Q4) are F. Further preferred compounds of formula Q, Q1 and Q2 arethose wherein L^(Q3), L^(Q4) and one or two of L^(Q1) and L^(Q2) are F.

Further preferred compounds of formula Q are those wherein X^(Q) denotesF or OCF₃, very preferably F.

The compounds of formula Q are preferably selected from the followingsubformulae

wherein R^(Q) has one of the meanings of formula Q or one of itspreferred meanings given above and below, and is preferably ethyl,n-propyl or n-butyl.

Preferred compounds of formula Q, Q1 and Q2 are those wherein R^(Q)denotes straight-chain alkyl with 2 to 6 C-atoms, very preferably ethyl,n-propyl or n-butyl.

Especially preferred are compounds of formula Q1, in particular thosewherein R^(Q) is n-propyl.

Preferably the proportion of compounds of formula Q in the LC medium,preferably in component B) of the LC medium, is from >0 to ≦5%, verypreferably from 0.05 to 2%, most preferably from 0.1 to 1%.

Preferably the LC medium contains 1 to 5, preferably 1 or 2 compounds offormula Q.

In the LC medium according to the present invention, the use of an LChost mixture comprising compounds of formula B and Q together with theuse of a polymerizable component comprising preferably direactive and/ortrireactive RMs, leads to advantageous properties in PSA displays. Inparticular, one or more of the following advantages could be achieved:

-   -   good UV absorption also at longer wavelengths,    -   quick and complete polymerisation of the RMs,    -   quick generation of a low pretilt angle, especially already at        low UV energy and/or at longer UV wavelengths,    -   high UV absorption,    -   increased UV stability,    -   high pretilt angle stability after UV exposure,    -   reduced image sticking,    -   reduced ODF mura,    -   high reliability and high VHR value after UV exposure and/or        heat treatment,    -   high birefringence,    -   reduced viscosity    -   faster response times.

It was surprisingly found that especially in LC media according to thepresent invention containing a higher amount of compounds of formula B,preferably at least 3% or even 4%, the VHR can be more significantlyimproved, e.g. the VHR can be maintained at high level even afterpolymerization of the polymerizable compound, by adding a compound offormula Q. Since the addition of a higher amount of compounds of formulaB leads to a more significantly improvement (i.e. reduction) of theviscosity, the addition of both a compound of formula B and a compoundof formula Q allows to combine the advantages of high VHR and reducedviscosity.

Moreover, the LC medium according to the present invention shows highabsorption at longer UV wavelengths, and thus enables using longer UVwavelengths for polymerization, which is advantageous for the displaymanufacturing process.

The polymerizable compounds are preferably selected from formula I

R^(a)—B¹—(Z^(b)—B²)_(m)—R^(b)   I

in which the individual radicals, on each occurrence identically ordifferently, and each, independently of one another, have the followingmeaning:

-   R^(a) and R^(b) P, P-Sp-, H, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS,    —OCN, —SCN, SF₅ or straight-chain or branched alkyl having 1 to 25 C    atoms, in which, in addition, one or more non-adjacent CH₂ groups    may each be replaced, independently of one another, by    —C(R⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰⁰)—, —O—, —S—, —CO—, —CO—O—, —O—CO—,    —O—CO—O— in such a way that O and/or S atoms are not linked directly    to one another, and in which, in addition, one or more H atoms may    be replaced by F, Cl, Br, I, CN, P or P-Sp-, where, if B¹ and/or B²    contain a saturated C atom, R^(a) and/or R^(b) may also denote a    radical which is spiro-linked to this saturated C atom,-   wherein at least one of the radicals R^(a) and R^(b) denotes or    contains a group P or P-Sp-,-   P a polymerizable group,-   Sp a spacer group or a single bond,-   B¹ and B² an aromatic, heteroaromatic, alicyclic or heterocyclic    group, preferably having 4 to 25 ring atoms, which may also contain    fused rings, and which is unsubstituted, or mono- or polysubstituted    by L,-   Z^(b) —O—, —S—, —CO—, —CO—O—, —OCO—, —O—CO—O—, —OCH₂—, —CH₂O—,    —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —(CH₂)_(n1)—,    —CF₂CH₂—, —CH₂CF₂—, —(CF₂)_(n1)—, —CH═CH—, —CF═CF—, —C≡C—,    —CH═CH—COO—, —OCO—CH═CH—, CR⁰R⁰⁰ or a single bond,-   R⁰ and R⁰⁰ each, independently of one another, denote H or alkyl    having 1 to 12 C atoms,-   m denotes 0, 1, 2, 3 or 4,-   n1 denotes 1, 2, 3 or 4,-   L P, P-Sp-, OH, CH₂OH, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS, —OCN,    —SCN, —C(═O)N(R^(x))₂, —C(═O)Y¹, —C(═O)R^(x), —N(R^(x))₂, optionally    substituted silyl, optionally substituted aryl having 6 to 20 C    atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl,    alkoxycarbonyl, alkylcarbonyloxy or alkoxy-carbonyloxy having 1 to    25 C atoms, in which, in addition, one or more H atoms may be    replaced by F, Cl, P or P-Sp-,-   P and Sp have the meanings indicated above,-   Y¹ denotes halogen,-   R^(x) denotes P, P-Sp-, H, halogen, straight-chain, branched or    cyclic alkyl having 1 to 25 C atoms, in which, in addition, one or    more non-adjacent CH₂ groups may be replaced by —O—, —S—, —CO—,    —CO—O—, —O—CO—, —O—CO—O— in such a way that O and/or S atoms are not    linked directly to one another, and in which, in addition, one or    more H atoms may be replaced by F, Cl, P or P-Sp-, an optionally    substituted aryl or aryloxy group having 6 to 40 C atoms, or an    optionally substituted heteroaryl or hetero-aryloxy group having 2    to 40 C atoms.

Particularly preferred compounds of the formula I are those in which B¹and B² each, independently of one another, denote 1,4-phenylene,1,3-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl,phenanthrene-2,7-diyl, 9,10-dihydro-phenanthrene-2,7-diyl,anthracene-2,7-diyl, fluorene-2,7-diyl, coumarine, flavone, where, inaddition, one or more CH groups in these groups may be replaced by N,cyclohexane-1,4-diyl, in which, in addition, one or more non-adjacentCH₂ groups may be replaced by O and/or S, 1,4-cyclohexenylene,bicycle[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl,spiro[3.3]heptane-2,6-diyl, piperidine-1,4-diyl,decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl,indane-2,5-diyl or octahydro-4,7-methanoindane-2,5-diyl, where all thesegroups may be unsubstituted or mono- or polysubstituted by L as definedabove.

Particularly preferred compounds of the formula I are those in which B¹and B² each, independently of one another, denote 1,4-phenylene,1,3-phenylene, naphthalene-1,4-diyl or naphthalene-2,6-diyl.

Very preferred compounds of formula I are selected from the followingformulae:

in which the individual radicals, on each occurrence identically ordifferently, and each, independently of one another, have the followingmeaning:

-   P¹, P², P³ a vinyloxy, acrylate, methacrylate, fluoroacrylate,    chloro-acrylate, oxetane or epoxy group,-   Sp¹, Sp², Sp³ a single bond or a spacer group where, in addition,    one or more of the radicals P¹-Sp¹-, P²-Sp²- and P³-Sp³- may denote    R^(aa), with the proviso that at least one of the radicals P¹-Sp¹-,    P²-Sp² and P³-Sp³- present is different from R^(aa),

R^(aa) H, F, Cl, CN or straight-chain or branched alkyl having 1 to 25 Catoms, in which, in addition, one or more non-adjacent CH₂ groups mayeach be replaced, independently of one another, by C(R⁰)═C(R⁰⁰)—, —C≡C—,—N(R⁰)—, —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a way that Oand/or S atoms are not linked directly to one another, and in which, inaddition, one or more H atoms may be replaced by F, Cl, CN or P¹-Sp¹-,particularly preferably straight-chain or branched, optionally mono- orpolyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 Catoms (where the alkenyl and alkynyl radicals have at least two C atomsand the branched radicals have at least three C atoms),

-   R⁰, R⁰⁰ H or alkyl having 1 to 12 C atoms,-   R^(y) and R^(z) H, F, CH₃ or CF₃,-   X¹, X², X³ —CO—O—, —O—CO— or a single bond,-   Z¹ —O—, —CO—, —C(R^(y)R^(z))— or —CF₂CF₂—,-   Z², Z³ —CO—O—, —O—CO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂— or    —(CH₂)_(n)—, where n is 2, 3 or 4,-   L F, Cl, CN or straight-chain or branched, optionally mono- or    polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,    alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12    C atoms,-   L′, L″ H, F or Cl,-   r 0, 1, 2, 3 or 4,-   s 0, 1, 2 or 3,-   t 0, 1 or 2,-   x 0 or 1.

Very preferred are compounds of formulae M2 and M13, especiallydireactive compounds containing exactly two polymerizable groups P¹ andP².

Further preferred are compounds M15 to M31, in particular M17, M18, M19,M22, M23, M24, M25, M26, M30 and M31, especially trireactive compoundscontaining exactly three polymerizable groups P¹, P² and/or P³.

In the compounds of formulae M1 to M31 the group

is preferably

wherein L on each occurrence, identically or differently, has one of themeanings given above or below, and is preferably F, Cl, CN, NO₂, CH₃,C₂H₅, C(CH₃)₃, CH(CH₃)₂, CH₂CH(CH₃)C₂H₅, OCH₃, OC₂H₅, COCH₃, COC₂H₅,COOCH₃, COOC₂H₅, CF₃, OCF₃, OCHF₂, OC₂F₅ or P-Sp-, very preferably F,Cl, CN, CH₃, C₂H₅, OCH₃, COCH₃, OCF₃ or P-Sp-, more preferably F, Cl,CH₃, OCH₃, COCH₃ orOCF₃ , especially F or CH₃.

Preferred compounds of formulae M1 to M30 are those wherein P¹, P² andP³ denote an acrylate, methacrylate, oxetane or epoxy group, verypreferably an acrylate or methacrylate group.

Further preferred compounds of formulae M1 to M31 are those wherein Sp¹,Sp² and Sp³ are a single bond.

Further preferred compounds of formulae M1 to M31 are those wherein oneof Sp¹, Sp² and Sp³ is a single bond and another one of Sp¹, Sp² and Sp³is different from a single bond.

Further preferred compounds of formulae M1 to M31 are those whereinthose groups Sp¹, Sp² and Sp³ that are different from a single bonddenote —(CH₂)_(s1)—X″—, wherein s1 is an integer from 1 to 6, preferably2, 3, 4 or 5, and X″ is the linkage to the benzene ring and is —O—,—O—CO—, —CO—O, —O—CO—O— or a single bond.

Particular preference is given to LC media comprising one, two or threepolymerizable compounds of formula I.

Preferably the proportion of compounds of formula I in the LC medium isfrom 0.01 to 5%, very preferably from 0.05 to 1%, most preferably from0.1 to 0.5%.

It was observed that, the combination of polymerizable compounds offormulae M1 to M31 with the compounds of formula B and Q leads toadvantageous behavior of the LC medium, where a quick andcompletepolymerization, the quick generation of a low pretilt anglewhich is stable after UV exposure, at the same time a high reliabilityand high VHR value after UV exposure can be achieved together with ahigh birefringence. Besides, the LC medium shows high absorption atlonger UV wavelengths, so that it is possible to use such longer UVwavelengths forpolymerization, which is advantageous for the displaymanufacturing process.

For the production of PSA displays, the polymerizable compoundscontained in the LC medium are polymerized or crosslinked (if onecompound contains two or more polymerizable groups) by in-situpolymerisation in the LC medium between the substrates of the LCdisplay, optionally while a voltage is applied to the electrodes.

The structure of the PSA displays according to the invention correspondsto the usual geometry for PSA displays, as described in the prior artcited at the outset. Geometries without protrusions are preferred, inparticular those in which, in addition, the electrode on the colourfilter side is unstructured and only the electrode on the TFT side hasslots. Particularly suitable and preferred electrode structures forPS-VA displays are described, for example, in US 2006/0066793 A1.

A preferred PSA type LC display of the present invention comprises:

-   -   a first substrate including a pixel electrode defining pixel        areas, the pixel electrode being connected to a switching        element disposed in each pixel area and optionally including a        micro-slit pattern, and optionally a first alignment layer        disposed on the pixel electrode,    -   a second substrate including a common electrode layer, which may        be disposed on the entire portion of the second substrate facing        the first substrate, and optionally a second alignment layer,    -   an LC layer disposed between the first and second substrates and        including an LC medium comprising a polymerizable component A        and a liquid crystal component B as described above and below,        wherein the polymerizable component A may also be polymerized.

The first and/or second alignment layer controls the alignment directionof the LC molecules of the LC layer. For example, in PS-VA displays thealignment layer is selected such that it imparts to the LC moleculeshomeotropic (or vertical) alignment (i.e. perpendicular to the surface)or tilted alignment. Such an alignment layer may for example comprise apolyimide, which may also be rubbed, or may be prepared by aphotoalignment method.

The LC layer with the LC medium can be deposited between the substratesof the display by methods that are conventionally used by displaymanufacturers, for example the so-called one-drop-filling (ODF) method.The polymerizable component of the LC medium is then polymerized forexample by UV photopolymerization. The polymerization can be carried outin one step or in two or more steps.

The PSA display may comprise further elements, like a color filter, ablack matrix, a passivation layer, optical retardation layers,transistor elements for addressing the individual pixels, etc., all ofwhich are well known to the person skilled in the art and can beemployed without inventive skill.

The electrode structure can be designed by the skilled person dependingon the individual display type. For example for PS-VA displays amulti-domain orientation of the LC molecules can be induced by providingelectrodes having slits and/or bumps or protrusions in order to createtwo, four or more different tilt alignment directions.

Upon polymerisation the polymerizable compounds form a crosslinkedpolymer, which causes a certain pretilt of the LC molecules in the LCmedium. Without wishing to be bound to a specific theory, it is believedthat at least a part of the crosslinked polymer, which is formed by thepolymerizable compounds, will phase-separate or precipitate from the LCmedium and form a polymer layer on the substrates or electrodes, or thealignment layer provided thereon. Microscopic measurement data (like SEMand AFM) have confirmed that at least a part of the formed polymeraccumulates at the LC/substrate interface.

The polymerization can be carried out in one step. It is also possiblefirstly to carry out the polymerization, optionally while applying avoltage, in a first step in order to produce a pretilt angle, andsubsequently, in a second polymerization step without an appliedvoltage, to polymerize or crosslink the compounds which have not reactedin the first step (“end curing”).

Suitable and preferred polymerization methods are, for example, thermalor photopolymerization, preferably photopolymerization, in particular UVinduced photopolymerization, which can be achieved by exposure of thepolymerizable compounds to UV radiation.

Optionally one or more polymerization initiators are added to the LCmedium. Suitable conditions for the polymerization and suitable typesand amounts of initiators are known to the person skilled in the art andare described in the literature. Suitable for free-radicalpolymerization are, for example, the commercially availablephotoinitiators Irgacure651®, Irgacure184®, Irgacure907®, Irgacure369®or Darocure1173® (Ciba AG). If a polymerization initiator is employed,its proportion is preferably 0.001 to 5% by weight, particularlypreferably 0.001 to 1% by weight.

The polymerizable compounds according to the invention are also suitablefor polymerization without an initiator, which is accompanied byconsiderable advantages, such, for example, lower material costs and inparticular less contamination of the LC medium by possible residualamounts of the initiator or degradation products thereof. Thepolymerization can thus also be carried out without the addition of aninitiator. In a preferred embodiment, the LC medium thus does notcontain a polymerization initiator.

The LC medium may also comprise one or more stabilisers in order toprevent undesired spontaneous polymerisation of the RMs, for exampleduring storage or transport. Suitable types and amounts of stabilisersare known to the person skilled in the art and are described in theliterature. Particularly suitable are, for example, the commerciallyavailable stabilisers from the Irganox® series (Ciba AG), such as, forexample, Irganox® 1076. If stabilisers are employed, their proportion,based on the total amount of RMs or the polymerizable component(component A), is preferably 10-500,000 ppm, particularly preferably50-50,000 ppm.

The polymerizable compounds of formula I do in particular show good UVabsorption in, and are therefore especially suitable for, a process ofpreparing a PSA display including one or more of the following features:

-   -   the polymerizable medium is exposed to UV light in the display        in a 2-step process, including a first UV exposure step (“UV-1        step”) to generate the tilt angle, and a second UV exposure step        (“UV-2 step”) to finish polymerization,    -   the polymerizable medium is exposed to UV light in the display        generated by an energy-saving UV lamp (also known as “green UV        lamps”). These lamps are characterized by a relative low        intensity ( 1/100- 1/10 of a conventional UV1 lamp) in their        absorption spectra from 300-380 nm, and are preferably used in        the UV2 step, but are optionally also used in the UV1 step when        avoiding high intensity is necessary for the process.    -   the polymerizable medium is exposed to UV light in the display        generated by a UV lamp with a radiation spectrum that is shifted        to longer wavelengths, preferably 340 nm or more, to avoid short        UV light exposure in the PS-VA process.

Both using lower intensity and a UV shift to longer wavelengths protectthe organic layer against damage that may be caused by the UV light.

A preferred embodiment of the present invention relates to a process forpreparing a PSA display as described above and below, comprising one ormore of the following features:

-   -   the polymerizable LC medium is exposed to UV light in a 2-step        process, including a first UV exposure step (“UV-1 step”) to        generate the tilt angle, and a second UV exposure step (“UV-2        step”) to finish polymerisation,    -   the polymerizable LC medium is exposed to UV light generated by        a UV lamp having an intensity of from 0.5 mW/cm² to 10 mW/cm² in        the wavelength range from 300-380 nm, preferably used in the UV2        step, and optionally also in the UV1 step,    -   the polymerizable LC medium is exposed to UV light having a        wavelength of 340 nm or more, and preferably 400 nm or less.

This preferred process can be carried out for example by using thedesired UV lamps or by using a band pass filter and/or a cut-off filter,which are substantially transmissive for UV light with the respectivedesired wavelength(s) and are substantially blocking light with therespective undesired wavelengths. For example, when irradiation with UVlight of wavelengths λ of 300-400 nm is desired, UV exposure can becarried out using a wide band pass filter being substantiallytransmissive for wavelengths 300 nm<λ<400 nm. When irradiation with UVlight of wavelength λ of more than 340 nm is desired, UV exposure can becarried out using a cut-off filter being substantially transmissive forwavelengths λ>340 nm.

“Substantially transmissive” means that the filter transmits asubstantial part, preferably at least 50% of the intensity, of incidentlight of the desired wavelength(s). “Substantially blocking” means thatthe filter does not transmit a substantial part, preferably at least 50%of the intensity, of incident light of the undesired wavelengths.“Desired (undesired) wavelength” e.g. in case of a band pass filtermeans the wavelengths inside (outside) the given range of λ, and in caseof a cut-off filter means the wavelengths above (below) the given valueof λ.

This preferred process enables the manufacture of displays by usinglonger UV wavelengths, thereby reducing or even avoiding the hazardousand damaging effects of short UV light components.

UV radiation energy is in general from 6 to 100 J, depending on theproduction process conditions.

Preferably the LC medium according to the present invention doesessentially consist of a polymerizable component A) and an LC componentB) (or LC host mixture) as described above and below. However, the LCmedium may additionally comprise one or more further components oradditives, preferably selected from the list including but not limitedto co-monomers, chiral dopants, polymerisation initiators, inhibitors,stabilizers, surfactants, wetting agents, lubricating agents, dispersingagents, hydrophobing agents, adhesive agents, flow improvers, defoamingagents, deaerators, diluents, reactive diluents, auxiliaries,colourants, dyes, pigments and nanoparticles.

Preference is given to LC media in which the polymerizable component A)consists exclusively of polymerizable compounds of formula I.

In another preferred embodiment the polymerizable component A) contains,in addition to the compounds of formula I, one or more furtherpolymerizable compounds (“co-monomers”), preferably selected from RMs.

Preferably the proportion of the polymerizable component A) in the LCmedium is from >0 to <5%, very preferably from >0 to ≦1%, mostpreferably from 0.01 to 0.5%.

Preferably the proportion of the LC component B) in the LC medium isfrom 95 to <100%, very preferably from 99 to <100%.

Besides the polymerizable component A) as described above, the LC mediaaccording to the present invention comprise an LC component B), or LChost mixture, comprising one or more, preferably two or more LCcompounds which are selected from low-molecular-weight compounds thatare unpolymerizable. These LC compounds are selected such that they arestable and/or unreactive to a polymerization reaction under theconditions applied to the polymerization of the polymerizable compounds.

Examples of these compounds are the aforementioned compounds of formulaeB and Q.

Preference is given to LC media in which the LC component B), or the LChost mixture, has a nematic LC phase, and preferably has no chiralliquid crystal phase.

Preference is furthermore given to achiral compounds of formula I, andto LC media in which the compounds of component A and/or B are selectedexclusively from the group consisting of achiral compounds.

The LC component B), or LC host mixture, is preferably a nematic LCmixture.

In a preferred embodiment of the present invention the LC component B),or LC host mixture, of the LC medium comprises, in addition to thecompounds of formula A, one or more further mesogenic or LC compoundscomprising a straight-chain, branched or cyclic alkenyl group(hereinafter also referred to as “alkenyl compounds”), wherein saidalkenyl group is stable to a polymerisation reaction under theconditions used for polymerization of the polymerizable compoundscontained in the LC medium.

These further alkenyl compounds are preferably selected from formula ANand AY

in which the individual radicals, on each occurrence identically ordifferently, and each, independently of one another, have the followingmeaning:

is

is

is

-   R^(A1) alkenyl having 2 to 9 C atoms or, if at least one of the    rings X, Y and Z denotes cyclohexenyl, also one of the meanings of    R^(A2),-   R^(A2) alkyl having 1 to 12 C atoms, in which, in addition, one or    two non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,    —OCO— or —COO— in such a way that O atoms are not linked directly to    one another,-   Z^(x) —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—,    —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O—, or a single bond, preferably    a single bond,-   L¹⁻⁴ H, F, Cl, OCF₃, CF₃, CH₃, CH₂F or CHF₂H, preferably H, F or Cl,-   x 1 or 2,-   z 0 or 1.

Preferred compounds of formula AN and AY are those wherein R^(A2) isselected from ethenyl, propenyl, butenyl, pentenyl, hexenyl andheptenyl.

Further preferred compounds of formula AN and AY are those wherein L¹and L² denote F, or one of L¹ and L² denotes F and the other denotes Cl,and L³ and L⁴ denote F, or one of L³ and L⁴ denotes F and the otherdenotes Cl.

The compounds of the formula AN are preferably selected from thefollowing sub-formulae:

in which alkyl and alkyl* each, independently of one another, denote astraight-chain alkyl radical having 1-6 C atoms, and alkenyl andalkenyl* each, independently of one another, denote a straight-chainalkenyl radical having 2-7 C atoms. Alkenyl and alkenyl* preferablydenote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—,CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

Very preferred compounds of the formula AN are selected from thefollowing sub-formulae:

in which m denotes 1, 2, 3, 4, 5 or 6, i denotes 0, 1, 2 or 3, andR^(b1) denotes H, CH₃ or C₂H₅.

Very particularly preferred compounds of the formula AN are selectedfrom the following sub-formulae:

Most preferred are compounds of formula AN1a2, AN1a5, AN6a1 and AN6a2.

The compounds of the formula AY are preferably selected from thefollowing sub-formulae:

in which alkyl and alkyl* each, independently of one another, denote astraight-chain alkyl radical having 1-6 C atoms, and alkenyl andalkenyl* each, independently of one another, denote a straight-chainalkenyl radical having 2-7 C atoms. Alkenyl and alkenyl* preferablydenote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—,CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

Very preferred compounds of the formula AY are selected from thefollowing sub-formulae:

in which m and n each, independently of one another, denote 1, 2, 3, 4,5 or 6, and alkenyl denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— orCH₃—CH═CH—(CH₂)₂—.

The LC medium preferably comprises no compounds containing a terminalvinyloxy group (—O—CH═CH₂), in particular no compounds of the formula ANor AY in which R^(A1) or R^(A2) denotes or contains a terminal vinyloxygroup (—O—CH═CH₂).

In a preferred embodiment the LC medium contains an LC component B), orLC host mixture, based on compounds with negative dielectric anisotropy.Such LC media are especially suitable for use in PS-VA and PS-UB-FFSdisplays. Particularly preferred embodiments of such an LC medium, andof the corresponding LC component B) or LC host mixture, are those ofsections a)-y) below:

-   a) The LC medium or LC host mixture comprises one or more compounds    of the formulae CY and/or PY:

-   -   wherein    -   a denotes 1 or 2,    -   b denotes 0 or 1,

denotes

-   -   R¹ and R² each, independently of one another, denote alkyl        having 1 to 12 C atoms, where, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —OCO— or —COO— in such a way that O atoms are not linked        directly to one another, preferably alkyl or alkoxy having 1 to        6 C atoms,    -   Z^(x) and Z^(y) each, independently of one another, denote        —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—,        —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,        preferably a single bond,    -   L¹⁻⁴ each, independently of one another, denote F, Cl, OCF₃,        CF₃, CH₃, CH₂F, CHF₂.    -   Preferably, both L¹ and L² denote F or one of L¹ and L² denotes        F and the other denotes Cl, or both L³ and L⁴ denote F or one of        L³ and L⁴ denotes F and the other denotes Cl.    -   The compounds of the formula CY are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms,        and (O) denotes an oxygen atom or a single bond. Alkenyl        preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   The compounds of the formula PY are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms,        and (O) denotes an oxygen atom or a single bond. Alkenyl        preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.

-   b) The LC medium or LC host mixture comprises one or more compounds    of the following formula:

-   -   in which the individual radicals have the following meanings:

denotes

denotes

-   -   R³ and R⁴ each, independently of one another, denote alkyl        having 1 to 12 C atoms, in which, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —O—CO— or —CO—O— in such a way that O atoms are not linked        directly to one another,    -   Z^(y) denotes —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,        —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,        preferably a single bond.    -   The compounds of the formula ZK are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl denotes a straight-chain alkenyl radical having 2-6 C        atoms. Alkenyl preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—,        CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH—        or CH₃—CH═CH—(CH₂)₂—.    -   Especially preferred are compounds of formula ZK1.    -   Particularly preferred compounds of formula ZK are selected from        the following sub-formulae:

-   -   wherein the propyl, butyl and pentyl groups are straight-chain        groups.    -   Most preferred are compounds of formula ZK1a.

-   c) The LC medium or LC host mixture comprises one or more compounds    of the following formula:

-   -   in which the individual radicals on each occurrence, identically        or differently, have the following meanings:    -   R⁵ and R⁶ each, independently of one another, denote alkyl        having 1 to 12 C atoms, where, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —OCO— or —COO— in such a way that O atoms are not linked        directly to one another, preferably alkyl or alkoxy having 1 to        6 C atoms,

denotes

denotes

and

-   -   e denotes 1 or 2.    -   The compounds of the formula DK are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl denotes a straight-chain alkenyl radical having 2-6 C        atoms. Alkenyl preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—,        CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH—        or CH₃—CH═CH—(CH₂)₂—.

-   d) The LC medium or LC host mixture comprises one or more compounds    of the following formula:

-   -   in which the individual radicals have the following meanings:

denotes

-   -   with at least one ring F being different from cyclohexylene,    -   f denotes 1 or 2,    -   R¹ and R² each, independently of one another, denote alkyl        having 1 to 12 C atoms, where, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —OCO— or —COO— in such a way that O atoms are not linked        directly to one another,    -   Z^(x) denotes —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,        —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,        preferably a single bond.    -   L¹ and L² each, independently of one another, denote F, Cl,        OCF₃, CF₃, CH₃, CH₂F, CHF₂.    -   Preferably, both radicals L¹ and L² denote F or one of the        radicals L¹ and L² denotes F and the other denotes Cl.    -   The compounds of the formula LY are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which R¹ has the meaning indicated above, alkyl denotes a        straight-chain alkyl radical having 1-6 C atoms, (O) denotes an        oxygen atom or a single bond, and v denotes an integer from 1        to 6. R¹ preferably denotes straight-chain alkyl having 1 to 6 C        atoms or straight-chain alkenyl having 2 to 6 C atoms, in        particular CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, n-C₅H₁₁, CH₂═CH—,        CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—,        CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

-   e) The LC medium or LC host mixture comprises one or more compounds    of the following formula:

-   -   in which the individual radicals, on each occurrence identically        or differently, and each, independently of one another, have the        following meaning:    -   R¹, R² alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C        atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of        which are optionally fluorinated,    -   L^(T1)-L^(T6) H, F or Cl, with at least one of L^(T1) to L^(T6)        being F or Cl,    -   The compounds of the formula T are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which R denotes a straight-chain alkyl or alkoxy radical        having 1-7 C atoms, R* denotes a straight-chain alkenyl radical        having 2-7 C atoms, (O) denotes an oxygen atom or a single bond,        and m denotes an integer from 1 to 6. R* preferably denotes        CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—,        CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.    -   R and R* preferably denote methyl, ethyl, propyl, butyl, pentyl,        hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.    -   Very preferred are compounds of formulae T1, T2 and T3,        especially those of formula T1 and T2.    -   Very preferred are compounds of formula T1-T24 wherein (O)        denotes an oxygen atom, m is 1, 2, 3, 4 or 5 and R is methyl,        ethyl, propyl, butyl of pentyl or hexyl, which are preferably        straight-chained.    -   Preferably, the LC medium does not contain more than 15% of        compounds of formula T or T1-T24 or any other compounds with a        terphenyl group.    -   Preferably the proportion of compounds of formula T or T1-T24 or        any other compounds with a terphenyl group in the LC medium is        at least 5%, very preferably from 5 to 15%, most preferably from        5 to 10%.    -   Preferably the LC medium contains 1 to 5, very preferably 1 or 2        compounds of formula T or T1-T24.

-   f) The LC medium or LC host mixture comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which alkyl denotes C₁₋₆-alkyl, L^(x) denotes H or F, and X        denotes F, Cl, OCF₃, OCHF₂ or OCH═CF₂. Particular preference is        given to compounds of the formula G1 in which X denotes F.

-   g) The LC medium or LC host mixture comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which R⁵ has one of the meanings indicated above for R¹,        alkyl denotes C₁₋₆-alkyl, d denotes 0 or 1, and z and m each,        independently of one another, denote an integer from 1 to 6. R⁵        in these compounds is particularly preferably C₁₋₆-alkyl or        -alkoxy or C₂₋₆-alkenyl, d is preferably 1. The LC medium        according to the invention preferably comprises one or more        compounds of the above-mentioned formulae in amounts of ≧5% by        weight.

-   h) The LC medium or LC host mixture comprises one or more biphenyl    compounds selected from the group consisting of the following    formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   The proportion of the biphenyls of the formulae B1 to B3 in the        LC mixture is preferably at least 3% by weight, in particular        ≧5% by weight.    -   The compounds of the formula B2 are particularly preferred.    -   The compounds of the formulae B1 to B3 are preferably selected        from the group consisting of the following sub-formulae:

-   -   in which alkyl* denotes an alkyl radical having 1-6 C atoms. The        medium according to the invention particularly preferably        comprises one or more compounds of the formulae B1a and/or B2c.

-   i) The LC medium or LC host mixture comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which R¹ and R² have the meanings indicated above and        preferably each, independently of one another, denote        straight-chain alkyl having 1 to 6 C atoms or straight-chain        alkenyl having 2 to 6 C atoms.    -   Preferred media comprise one or more compounds selected from the        formulae O1, O3 and O4.

-   k) The LC medium or LC host mixture comprises one or more compounds    of the following formula:

-   -   in which

denotes

-   -   R⁹ denotes H, CH₃, C₂H₅ or n-C₃H₇, (F) denotes an optional        fluorine substituent, and q denotes 1, 2 or 3, and R⁷ has one of        the meanings indicated for R¹, preferably in amounts of >3% by        weight, in particular ≧5% by weight and very particularly        preferably 5-30% by weight.    -   Particularly preferred compounds of the formula FI are selected        from the group consisting of the following sub-formulae:

-   -   in which R⁷ preferably denotes straight-chain alkyl, and R⁹        denotes CH₃, C₂H₅ or n-C₃H₇. Particular preference is given to        the compounds of the formulae FI1, FI2 and FI3.

-   l) The LC medium or LC host mixture comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which R⁸ has the meaning indicated for R¹, and alkyl denotes        a straight-chain alkyl radical having 1-6 C atoms.

-   m) The LC medium or LC host mixture comprises one or more compounds    which contain a tetrahydronaphthyl or naphthyl unit, such as, for    example, the compounds selected from the group consisting of the    following formulae:

-   -   in which    -   R¹⁰ and R¹¹ each, independently of one another, denote alkyl        having 1 to 12 C atoms, where, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —OCO— or —COO— in such a way that O atoms are not linked        directly to one another, preferably alkyl or alkoxy having 1 to        6 C atoms,    -   and R¹⁰ and R¹¹ preferably denote straight-chain alkyl or alkoxy        having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C        atoms, and    -   Z¹ and Z² each, independently of one another, denote —C₂H₄—,        —CH═CH—, —(CH₂)₄—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CH—CH₂CH₂—,        —CH₂CH₂CH═CH—, —CH₂O—, —OCH₂—, —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—,        —CF═CH—, —CH═CF—, —CH₂— or a single bond.

-   n) The LC medium or LC host mixture comprises one or more    difluoro-dibenzochromans and/or chromans of the following formulae:

-   -   in which    -   R¹¹ and R¹² each, independently of one another, have one of the        meanings indicated above for R¹¹,    -   ring M is trans-1,4-cyclohexylene or 1,4-phenylene,    -   Z^(m) —C₂H₄—, —CH₂O—, —OCH₂—, —CO—O— or —O—CO—,    -   c is 0, 1 or 2,    -   preferably in amounts of 3 to 20% by weight, in particular in        amounts of 3 to 15% by weight.    -   Particularly preferred compounds of the formulae BC, CR and RC        are selected from the group consisting of the following        sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, (O)        denotes an oxygen atom or a single bond, c is 1 or 2, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   Very particular preference is given to mixtures comprising one,        two or three compounds of the formula BC-2.

-   o) The LC medium or LC host mixture comprises one or more    fluorinated phenanthrenes and/or dibenzofurans of the following    formulae:

-   -   in which R¹¹ and R¹² each, independently of one another, have        one of the meanings indicated above for R¹¹, b denotes 0 or 1, L        denotes F, and r denotes 1, 2 or 3.    -   Particularly preferred compounds of the formulae PH and BF are        selected from the group consisting of the following        sub-formulae:

-   -   in which R and R′ each, independently of one another, denote a        straight-chain alkyl or alkoxy radical having 1-7 C atoms.

-   p) The LC medium or LC host mixture comprises one or more monocyclic    compounds of the following formula

-   -   wherein    -   R¹ and R² each, independently of one another, denote alkyl        having 1 to 12 C atoms, where, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —OCO— or —COO— in such a way that O atoms are not linked        directly to one another, preferably alkyl or alkoxy having 1 to        6 C atoms,    -   L¹ and L² each, independently of one another, denote F, Cl,        OCF₃, CF₃, CH₃, CH₂F, CHF₂.    -   Preferably, both L¹ and L² denote F or one of L¹ and L² denotes        F and the other denotes Cl,    -   The compounds of the formula Y are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which, Alkyl and Alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, Alkoxy        denotes a straight-chain alkoxy radical having 1-6 C atoms, and        Alkenyl and Alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        Alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   Particularly preferred compounds of the formula Y are selected        from the group consisting of the following sub-formulae:

-   -   wherein Alkoxy preferably denotes straight-chain alkoxy with 3,        4, or 5 C atoms.

-   q) The LC medium does not contain a compound which contains a    terminal vinyloxy group (—O—CH═CH₂).

-   r) The LC medium comprises 1 to 5, preferably 1, 2 or 3,    polymerizable compounds, preferably selected from formula I or    sub-formulae thereof.

-   s) In the LC medium the proportion of polymerizable compounds, in    particular of formula I or sub-formulae thereof, in the mixture as a    whole is 0.05 to 5%, preferably 0.1 to 1%.

-   t) The LC medium comprises 1 to 8, preferably 1 to 5, compounds of    the formulae CY1, CY2, PY1 and/or PY2. The proportion of these    compounds in the mixture as a whole is preferably 5 to 60%,    particularly preferably 10 to 35%. The content of these individual    compounds is preferably in each case 2 to 20%.

-   u) The LC medium comprises 1 to 8, preferably 1 to 5, compounds of    the formulae CY9, CY10, PY9 and/or PY10. The proportion of these    compounds in the mixture as a whole is preferably 5 to 60%,    particularly preferably 10 to 35%. The content of these individual    compounds is preferably in each case 2 to 20%.

-   v) The LC medium comprises 1 to 10, preferably 1 to 8, compounds of    the formula ZK, in particular compounds of the formulae ZK1, ZK2    and/or ZK6. The proportion of these compounds in the mixture as a    whole is preferably 3 to 25%, particularly preferably 5 to 45%. The    content of these individual compounds is preferably in each case 2    to 20%.

-   w) In the LC medium the proportion of compounds of formulae CY, PY    and ZK in the mixture as a whole is greater than 70%, preferably    greater than 80%.

-   x) The LC medium or LC host mixture contains one or more compounds    containing an alkenyl group, preferably selected from the group    consisting of formula CY, PY and LY, wherein one or both of R¹ and    R² denote straight-chain alkenyl having 2-6 C atoms, formula ZK and    DK, wherein one or both of R³ and R⁴ or one or both of R⁵ and R⁶    denote straight-chain alkenyl having 2-6 C atoms, and formula B2 and    B3, very preferably selected from formulae CY15, CY16, CY24, CY32,    PY15, PY16, ZK3, ZK4, DK3, DK6, B2 and B3. The concentration of    these compounds in the LC host mixture is preferably from 2 to 70%,    very preferably from 3 to 55%.

-   y) The LC medium contains one or more, preferably 1 to 5, compounds    selected of formula PY1-PY8, very preferably of formula PY2. The    proportion of these compounds in the mixture as a whole is    preferably 1 to 30%, particularly preferably 2 to 20%. The content    of these individual compounds is preferably in each case 1 to 20%.

The combination of compounds of the preferred embodiments mentionedabove with the polymerized compounds described above causes lowthreshold voltages, low rotational viscosities and very goodlow-temperature stabilities in the LC media according to the inventionat the same time as constantly high clearing points and high HR values,and allows the rapid establishment of a particularly low pretilt anglein PSA displays. In particular, the LC media exhibit significantlyshortened response times, in particular also the grey-shade responsetimes, in PSA displays compared with the media from the prior art.

The LC media and LC host mixtures according to the invention, whileretaining the nematic phase down to −20° C. and preferably down to −30°C., particularly preferably down to −40° C., and the clearing point ≧70°C., preferably ≧74° C., at the same time allow rotational viscosities γ₁of ≦120 mPa·s to be achieved, enabling excellent MLC displays havingfast response times to be achieved.

The LC media and LC host mixtures of the present invention preferablyhave a nematic phase range of at least 80 K, particularly preferably atleast 100 K, and a rotational viscosity ≦150 mPa·s, preferably ≦120mPa·s, at 20° C.

In the VA-type displays according to the invention, the molecules in thelayer of the LC medium in the switched-off state are alignedperpendicular to the electrode surfaces (homeotropically) or have atilted homeotropic alignment. On application of an electrical voltage tothe electrodes, a realignment of the LC molecules takes place with thelongitudinal molecular axes parallel to the electrode surfaces.

The LC media according to the invention, in particular for use indisplays of the PS-VA and PS-UB-FFS type, preferably have a negativedielectric anisotropy Ac, very preferably from −0.5 to −10, mostpreferably from −2.5 to −7.5, at 20° C. and 1 kHz.

The birefringence An in LC media according to the invention, inparticular for use in displays of the PS-VA and PS-UB-FFS type ispreferably below 0.16, very preferably from 0.06 to 0.14, mostpreferably from 0.07 to 0.12.

In order to increase the anchoring force, polymerizable compounds,so-called “reactive mesogens”, may also additionally be added to themixtures according to the invention. Preferred polymerizable compoundsare listed in Table D.

The LC media according to the invention may also comprise furtheradditives which are known to the person skilled in the art and aredescribed in the literature, such as, for example, polymerisationinitiators, inhibitors, stabilisers, surface-active substances or chiraldopants. These additives may be polymerizable or non-polymerizable.Polymerizable additives are accordingly ascribed to the polymerizablecomponent or component A). Non-polymerizable additives are accordinglyascribed to the non-polymerizable component or component B).

The LC media according to the present invention may, for example, alsocomprise one or more UV stabilisers, such as Tinuvin® from CibaChemicals, in particular Tinuvin® 770, antioxidants, free-radicalscavengers, nanoparticles, etc. Suitable stabilisers are mentioned belowin Tables C.

The LC media according to the present invention may, for example, alsocomprise one or more chiral dopants, preferably in a concentration from0.01 to 1%, very preferably from 0.05 to 0.5%. Suitable chiral dopantsare mentioned below in Table B. Preferred chiral dopants are for exampleselected from R- or S-1011, R- or S-2011, R- or S-3011, R- or S-4011, orR- or S-5011.

In another preferred embodiment the LC media contain a racemate of oneor more chiral dopants, which are preferably selected from the chiraldopants mentioned in the previous paragraph.

Furthermore, it is possible to add to the LC media, for example, 0 to15% by weight of pleochroic dyes, furthermore nanoparticles, conductivesalts, preferably ethyldimethyldodecylammonium 4-hexoxybenzoate,tetrabutylammonium tetraphenylborate or complex salts of crown ethers(cf., for example, Haller et al., Mol. Cryst. Liq. Cryst. 24, 249-258(1973)), for improving the conductivity, or substances for modifying thedielectric anisotropy, the viscosity and/or the alignment of the nematicphases. Substances of this type are described, for example, in DE-A 2209 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53728.

The individual components of the preferred embodiments a)-y) of the LCmedia according to the invention are either known or methods for thepreparation thereof can readily be derived from the prior art by theperson skilled in the relevant art, since they are based on standardmethods described in the literature. Compounds of the formula CY aredescribed, for example, in EP-A-0 364 538. Compounds of the formula ZKare described, for example, in DE-A-26 36 684 and DE-A-33 21 373.

It goes without saying to the person skilled in the art that the LCmedia according to the invention may also comprise compounds in which,for example, H, N, O, Cl, F have been replaced by the correspondingisotopes like deuterium etc.

The LC media which can be used in accordance with the invention areprepared in a manner conventional per se, for example by mixing one ormore compounds of the formula B and Q with one or more compounds of theabove-mentioned preferred embodiments and/or with furtherliquid-crystalline compounds and/or additives, like polymerizablecompounds or RMs. In general, the desired amount of the components usedin the smaller amount is dissolved in the components making up theprincipal constituent, advantageously at elevated temperature. It isalso possible to mix solutions of the components in an organic solvent,for example in acetone, chloroform or methanol, and to remove thesolvent again, for example by distillation, after thorough mixing.

It goes without saying that, through a suitable choice of the componentsof the LC mixtures according to the invention, it is also possible forhigher clearing points (for example above 100° C.) to be achieved athigher threshold voltages or lower clearing points to be achieved atlower threshold voltages with retention of the other advantageousproperties. At viscosities correspondingly increased only slightly, itis likewise possible to obtain mixtures having higher Δε and thus lowthresholds. The MLC displays according to the invention preferablyoperate at the first Gooch and Tarry transmission minimum [C. H. Goochand H. A. Tarry, Electron. Lett. 10, 2-4, 1974; C. H. Gooch and H. A.Tarry, Appl. Phys., Vol. 8, 1575-1584, 1975], where, besidesparticularly favorable electro-optical properties, such as, for example,high steepness of the characteristic line and low angle dependence ofthe contrast (German patent 30 22 818), lower dielectric anisotropy issufficient at the same threshold voltage as in an analogous display atthe second minimum. This enables significantly higher specificresistance values to be achieved using the mixtures according to theinvention at the first minimum than in the case of mixtures comprisingcyano compounds. Through a suitable choice of the individual componentsand their proportions by weight, the person skilled in the art is ableto set the birefringence necessary for a pre-specified layer thicknessof the MLC display using simple routine methods.

The construction of an LC display according to the invention frompolarisers, electrode base plates and surface-treated electrodescorresponds to the usual design for displays of this type. The termusual design is broadly drawn here and also encompasses all derivativesand modifications of the LC display, in particular including matrixdisplay elements based on poly-Si TFTs or MIM.

The following examples are intended to explain the invention withoutlimiting it. Above and below, percentage data denote per cent by weight;all temperatures are indicated in degrees Celsius.

Throughout the patent application and in the working examples, thestructures of the liquid-crystal compounds are indicated by means ofacronyms. Unless indicated otherwise, the transformation into chemicalformulae takes place in accordance with Tables I-III. All radicalsC_(n)H_(2n+1), C_(m)H_(2m+1), C_(n)H_(2n), C_(m)H_(2m) and C_(k)H_(2k)are straight-chain alkyl radicals or alkenyl radicals respectively, ineach case having n, m or k C atoms; n and m each, independently of oneanother, denote 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, preferably 1,2, 3, 4, 5 or 6, and k is 0, 1, 2, 3, 4, 5 or 6. In Table I the ringelements of the respective compound are coded, in Table II the bridgingmembers are listed and in Table III the meanings of the symbols for theleft-hand and right-hand side chains of the compounds are indicated.

TABLE I Ring elements

A

AI

B

B(S)

C

D

DI

F

FI

G

GI

K

L

LI

M

MI

N

NI

P

S

U

UI

Y

Y(F, Cl)

Y(Cl, F)

TABLE II Bridging members E —CH₂CH₂— V —CH═CH— T —C≡C— W —CF₂CF₂— Z—COO— ZI —OCO— O —CH₂O— OI —OCH₂— Q —CF₂O— QI —OCF₂—

TABLE III Side chains Left-hand side chain Right-hand side chain n-C_(n)H_(2n+1)— -n —C_(n)H_(2n+1) nO- C_(n)H_(2n+1)—O— -On—O—C_(n)H_(2n+1) V- CH₂═CH— -V —CH═CH₂ nV- C_(n)H_(2n+1)—CH═CH— -nV—C_(n)H_(2n)—CH═CH₂ Vn- CH₂═CH—C_(n)H_(2n)— -Vn —CH═CH—C_(n)H_(2n+1)nVm- C_(n)H_(2n+1)—CH═CH—C_(m)H_(2m)— -nVm—C_(n)H_(2n)—CH═CH—C_(m)H_(2m+1) N- N≡C— -N —C≡N F- F— -F —F Cl- Cl— -Cl—Cl M- CFH₂— -M —CFH₂ D- CF₂H— -D —CF₂H T- CF₃— -T —CF₃ MO- CFH₂O— -OM—OCFH₂ DO- CF₂HO— -OD —OCFH₂H TO- CF₃O— -OT —OCF₃ T- CF₃— -T —CF₃ A-H—C≡C— -A —C≡C—H FXO- CF₂═CHO— -OXF —OCH═CF₂

Preferred mixture components are shown in Table A.

In the formulae below m and n are independently of each other an integerfrom 1 to 12, preferably 1, 2, 3, 4, 5 or 6, k is 0, 1, 2, 3, 4, 5 or 6,and (O)C_(m)H_(2m+1) means C_(m)H_(2m+1) or OC_(m)H_(2m+1).

TABLE A

AIK-n-F

AIY-n-Om

AY-n-Om

B-nO—Om

B-n-Om

B(S)-nO—Om

B(S)-n-Om

CB(S)-n-(O)m

CB-n-m

CB-n-Om

PB-n-m

PB-n-Om

BCH-nm

BCH-nmF

BCN-nm

C-1V-V1

CY-n-Om

CY(F,Cl)-n-Om

CY(Cl,F)-n-Om

CCY-n-Om

CAIY-n-Om

CCY(F,Cl)-n-Om

CCY(Cl,F)-n-Om

CCY-n-m

CCY-V-m

CCY-Vn-m

CCY-n-OmV

CBC-nmF

CBC-nm

CCP-V-m

CCP-Vn-m

CCP-nV-m

CCP-n-m

CPYP-n-(O)m

CYYC-n-m

CCYY-n-(O)m

CCY-n-O2V

CCH-nOm

CCC-n-m

CCC-n-V

CY-n-m

CCH-nm

CC-n-V

CC-n-V1

CC-n-Vm

CC-V-V

CC-V-V1

CC-2V-V2

CVC-n-m

CC-n-mV

CC-n-mV1

CCOC-n-m

CP-nOmFF

CH-nm

CEY-n-Om

CEY-V-n

CVY-V-n

CY-V-On

CY-n-O1V

CY-n-OC(CH₃)═CH₂

CCN-nm

CY-n-OV

CCPC-nm

CCY-n-kOm

CPY-n-Om

CPY-n-m

CPY-V-Om

CQY-n-(O)m

CQIY-n-(O)m

CCQY-n-(O)m

CCQIY-n-(O)m

CPQY-n-(O)m

CPQIY-n-(O)m

CPYG-n-(O)m

CCY-V-Om

CCY-V2-(O)m

CCY-1V2-(O)m

CCY-3V-(O)m

CCVC-n-V

CCVC-V-V

CPGP-n-m

CY-nV-(O)m

CENaph-n-Om

COChrom-n-Om

COChrom-n-m

CCOChrom-n-Om

CCOChrom-n-m

CONaph-n-Om

CCONaph-n-Om

CCNaph-n-Om

CNaph-n-Om

CETNaph-n-Om

CTNaph-n-Om

CK-n-F

CLY-n-Om

CLY-n-m

LYLI-n-m

CYLI-n-m

LY-n-(O)m

COYOICC-n-m

COYOIC-n-V

CCOY-V-O2V

CCOY-V-O3V

COY-n-Om

CCOY-n-Om

CCEY-n-Om

CZYY-n-Om

D-nOmFF

PCH-nm

PCH-nOm

PGIGI-n-F

PGP-n-m

PP-n-m

PP-n-2V1

PPP-n-2V1

PGP-n-2V1

PGP-n-2V

PYP-n-mV

PYP-n-m

PGIY-n-Om

PYP-n-Om

PPYY-n-m

YPY-n-m

YPY-n-mV

PY-n-Om

PY-n-m

PY-V2-Om

DFDBC-n(O)—(O)m

Y-nO—Om

Y-nO—OmV

Y-nO—OkVm

YG-n-Om

YG-nO—Om

YGI-n-Om

YGI-nO—Om

YY-n-Om

YY-nO—Om

PPGU-n-F

Particular preference is given to liquid-crystalline mixtures whichcomprise at least one, two, three, four or more compounds from Table A.

Table B indicates possible dopants which are generally added to themixtures according to the invention. The mixtures preferably comprise0-10% by weight, in particular 0.001-5% by weight and particularlypreferably 0.001-3% by weight, of dopants.

TABLE B

C 15

CB 15

CM 21

R/S-811

CM 44

CM 45

CM 47

CN

R/S-2011

R/S-3011

R/S-4011

R/S-5011

R/S-1011

Stabilisers which can be added, for example, to the mixtures accordingto the invention in amounts of 0-10% by weight are mentioned below.

TABLE C

n = 1, 2, 3, 4, 5, 6 or 7

n = 1, 2, 3, 4, 5, 6 or 7

n = 1, 2, 3, 4, 5, 6 or 7

Table D shows illustrative reactive mesogenic compounds which can beused in the LC media in accordance with the present invention.

TABLE D

RM-1

RM-2

RM-3

RM-4

RM-5

RM-6

RM-7

RM-8

RM-9

RM-10

RM-11

RM-12

RM-13

RM-14

RM-15

RM-16

RM-17

RM-18

RM-19

RM-20

RM-21

RM-22

RM-23

RM-24

RM-25

RM-26

RM-27

RM-28

RM-29

RM-30

RM-31

RM-32

RM-33

RM-34

RM-35

RM-36

RM-37

RM-38

RM-39

RM-40

RM-41

RM-42

RM-43

RM-44

RM-45

RM-46

RM-47

RM-48

RM-49

RM-50

RM-51

RM-52

RM-53

RM-54

RM-55

RM-56

RM-57

RM-58

RM-59

RM-60

RM-61

RM-62

RM-63

RM-64

RM-65

RM-66

RM-67

RM-68

RM-69

RM-70

RM-71

RM-72

RM-73

RM-74

RM-75

RM-76

RM-77

RM-78

RM-79

RM-80

RM-81

RM-82

RM-83

RM-84

RM-85

RM-86

RM-87

RM-88

RM-89

RM-90

RM-91

RM-92

RM-93

RM-94

RM-95

RM-96

RM-97

RM-98

RM-99

RM-100

RM-101

RM-102

RM-103

RM-104

RM-105

RM-106

RM-107

RM-108

RM-109

RM-110

RM-111

RM-112

RM-113

RM-114

RM-115

RM-116

RM-117

RM-118

RM-119

RM-120

RM-121

RM-122

RM-123

RM-124

RM-125

RM-126

RM-127

RM-128

RM-129

RM-130

RM-131

In a preferred embodiment, the mixtures according to the inventioncomprise one or more polymerizable compounds, preferably selected fromthe polymerizable compounds of the formulae RM-1 to RM-131. Of these,compounds RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-43, RM-47,RM-49, RM-51, RM-59, RM-69, RM-71, RM-83, RM-97, RM-98, RM-104, RM-112,RM-115 and RM-116 are particularly preferred.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing and in the examples, all temperatures are set forthuncorrected in degrees Celsius and, all parts and percentages are byweight, unless otherwise indicated.

The entire disclosures of all applications, patents and publications,cited herein and of corresponding European application No. 16183932.9,filed Aug. 12, 2016 are incorporated by reference herein.

EXAMPLES

The following examples explain the present invention without restrictingit. However, they show the person skilled in the art preferred mixtureconcepts with compounds preferably to be employed and the respectiveconcentrations thereof and combinations thereof with one another. Inaddition, the examples illustrate which properties and propertycombinations are accessible.

In addition, the following abbreviations and symbols are used:

-   V₀ threshold voltage, capacitive [V] at 20° C.,-   n_(e) extraordinary refractive index at 20° C. and 589 nm,-   n_(o) ordinary refractive index at 20° C. and 589 nm,-   Δn optical anisotropy at 20° C. and 589 nm,-   ε_(⊥) dielectric permittivity perpendicular to the director at    20° C. and 1 kHz,-   ε_(|) dielectric permittivity parallel to the director at 20° C. and    1 kHz,-   Δε dielectric anisotropy at 20° C. and 1 kHz,-   cl.p., T(N,I) clearing point [° C.],-   γ₁ rotational viscosity at 20° C. [mPa·s],-   K₁ elastic constant, “splay” deformation at 20° C. [pN],-   K₂ elastic constant, “twist” deformation at 20° C. [pN],-   K₃ elastic constant, “bend” deformation at 20° C. [pN].

Unless explicitly noted otherwise, all concentrations in the presentapplication are quoted in per cent by weight and relate to thecorresponding mixture as a whole, comprising all solid orliquid-crystalline components, without solvents.

Unless explicitly noted otherwise, all temperature values indicated inthe present application, such as, for example, for the melting pointT(C,N), the transition from the smectic (S) to the nematic (N) phaseT(S,N) and the clearing point T(N,I), are quoted in degrees Celsius (°C.). M.p. denotes melting point, cl.p.=clearing point. Furthermore,C=crystalline state, N=nematic phase, S=smectic phase and I=isotropicphase. The data between these symbols represent the transitiontemperatures.

All physical properties are and have been determined in accordance with“Merck Liquid Crystals, Physical Properties of Liquid Crystals”, StatusNov. 1997, Merck KGaA, Germany, and apply for a temperature of 20° C.,and Δn is determined at 589 nm and Δε at 1 kHz, unless explicitlyindicated otherwise in each case.

The term “threshold voltage” for the present invention relates to thecapacitive threshold (V₀), also known as the Freedericks threshold,unless explicitly indicated otherwise. In the examples, the opticalthreshold may also, as generally usual, be quoted for 10% relativecontrast (V₁₀).

Unless stated otherwise, the process of polymerizing the polymerizablecompounds in the PSA displays as described above and below is carriedout at a temperature where the LC medium exhibits a liquid crystalphase, preferably a nematic phase, and most preferably is carried out atroom temperature (also abbreviated as “RT”).

Unless stated otherwise, methods of preparing test cells and measuringtheir electrooptical and other properties are carried out by the methodsas described hereinafter or in analogy thereto.

The display used for measurement of the capacitive threshold voltageconsists of two plane-parallel glass outer plates at a separation of 25μm, each of which has on the inside an electrode layer and an unrubbedpolyimide alignment layer on top, which effect a homeotropic edgealignment of the liquid-crystal molecules.

The display or test cell used for measurement of the tilt anglesconsists of two plane-parallel glass outer plates at a separation of 4μm, each of which has on the inside an electrode layer and a polyimidealignment layer on top, where the two polyimide layers are rubbedantiparallel to one another and effect a homeotropic edge alignment ofthe liquid-crystal molecules.

The polymerizable compounds are polymerized in the display or test cellby irradiation with UVA light of defined intensity for a prespecifiedtime, with a voltage simultaneously being applied to the display(usually 10 V to 30 V alternating current, 1 kHz). In the examples,unless indicated otherwise, a metal halide lamp and an intensity of 50mW/cm² is used for polymerisation. The intensity is measured using astandard UVA meter (Hoenle UV-meter high end with UVA sensor).

The tilt angle is determined by crystal rotation experiment(Autronic-Melchers TBA-105). A low value (i.e. a large deviation fromthe 90° angle) corresponds to a large tilt here.

The VHR value is measured as follows: 0.3% of a polymerizable monomericcompound is added to the LC host mixture, and the resultant mixture isintroduced into VA-VHR test cells which comprise an unrubbedVA-polyimide alignment layer. The LC-layer thickness d is approx. 6 μm,unless stated otherwise. The VHR value is determined before and after UVexposure at 1 V, 60 Hz, 64 μs pulse (measuring instrument:Autronic-Melchers VHRM-105).

LC Host Mixtures

Comparison Example 1A

The nematic LC host mixture C0 is formulated as follows.

BCH-32 9.00% cl.p. 74.7° C.    CC-3-V1 6.00% Δn 0.1105 CCH-301 3.00% Δε−3.3 CCH-34 8.00% ε_(||) 3.6 CCH-35 8.00% γ₁ 117 mPa s CCP-3-1 8.00%K₃/K₁ 1.12 CCY-3-O2 11.00% CPY-2-O2 4.50% CPY-3-O2 5.50% CY-3-O2 15.00%PCH-301 4.00% PY-3-O2 18.00%

The mixture does not contain a compound of formula B or Q.

Comparison Example 1B

The nematic LC host mixture C1 is formulated as follows.

BCH-32 10.50% cl.p. 75.0° C.    CC-3-V1 6.00% Δn 0.1109 CCH-301 3.00% Δε−3.3 CCH-34 9.00% ε_(||) 3.6 CCH-35 8.00% γ₁ 116 mPa s CCP-3-1 8.00%K₃/K₁ 1.12 CCY-3-O2 11.00% CPY-3-O2 6.50% CY-3-O2 15.00% PCH-301 3.00%PY-3-O2 18.00% B(S)-2O-O5 2.00%

The mixture contains a compound of formula B (B(S)-2O-O5), but does notcontain a compound of formula Q.

Example 1

The nematic LC host mixture N1 is formulated as follows.

BCH-32 9.50% cl.p. 75.0° C.    CC-3-V1 6.00% Δn 0.1115 CCH-301 3.00% Δε−3.3 CCH-34 9.00% ε_(||) 3.7 CCH-35 8.00% γ₁ 120 mPa s CCP-3-1 8.00%K₃/K₁ 1.10 CCY-3-O2 12.00% CPY-2-O2 3.50% CPY-3-O2 3.00% CY-3-O2 15.00%PCH-301 2.50% PY-3-O2 18.00% B(S)-2O-O5 2.00% PPGU-3-F 0.50%

The mixture contains a compound of formula B (B(S)-2O-O5) and a compoundof formula Q (PPGU-3-F).

Comparison Example C2

The nematic LC host mixture C2 is formulated as follows.

BCH-32 8.50% cl.p. 74.8° C.    CC-3-V1 6.00% Δn 0.1104 CCH-301 3.00% Δε−3.3 CCH-34 9.00% ε_(||) 3.6 CCH-35 8.00% γ₁ 114 mPa s CCP-3-1 8.00%K₃/K₁ 1.13 CCY-3-O2 11.00% CPY-3-O2 7.00% CY-3-O2 11.50% PCH-301 7.00%PY-3-O2 17.00% B(S)-2O-O5 4.00%

The mixture contains a compound of formula B (B(S)-2O-O5), but does notcontain a compound of formula Q.

Example 2

The nematic LC host mixture N2 is formulated as follows.

BCH-32 10.00% cl.p. 74.5° C.    CC-3-V1 6.00% Δn 0.1114 CCH-301 3.00% Δε−3.3 CCH-34 9.00% ε_(||) 3.7 CCH-35 8.00% γ₁ 114 mPa s CCP-3-1 8.00%K₃/K₁ 1.11 CCY-3-O2 11.00% CPY-3-O2 5.00% CY-3-O2 15.00% PCH-301 3.50%PY-3-O2 17.00% B(S)-2O-O5 4.00% PPGU-3-F 0.50%

The mixture contains a compound of formula B (B(S)-2O-O5) and a compoundof formula Q (PPGU-3-F).

Comparison Example C3

The nematic LC host mixture C3 is formulated as follows.

BCH-32 10.50% cl.p. 74.9° C.    CC-3-V1 6.00% Δn 0.1110 CCH-301 3.00% Δε−3.3 CCH-34 9.00% ε_(||) 3.6 CCH-35 8.00% γ₁ 112 mPa s CCP-3-1 8.00%K₃/K₁ 1.11 CCY-3-O2 11.00% CPY-3-O2 4.00% CY-3-O2 12.50% PCH-301 6.50%PY-3-O2 15.50% B(S)-2O-O4 2.00% B(S)-2O-O5 4.00%

The mixture contains two compounds of formula B (B(S)-2O-O4,B(S)-2O-O5), but does not contain a compound of formula Q.

Example 3

The nematic LC host mixture N3 is formulated as follows.

BCH-32 9.00% cl.p. 75.2° C.    CC-3-V1 6.00% Δn 0.1109 CCH-301 3.00% Δε−3.3 CCH-34 9.00% ε_(||) 3.7 CCH-35 8.00% γ₁ 112 mPa s CCP-3-1 8.00%K₃/K₁ 1.11 CCY-3-O2 11.00% CPY-3-O2 5.00% CY-3-O2 13.50% PCH-301 6.50%PY-3-O2 14.50% B(S)-2O-O4 2.00% B(S)-2O-O5 4.00% PPGU-3-F 0.50%

The mixture contains two compounds of formula B (B(S)-2O-O4, B(S)-2O-O5)and a compound of formula Q (PPGU-3-F).

Comparison Example C4

The nematic LC host mixture C4 is formulated as follows.

BCH-32 8.00% cl.p. 74.9° C. CC-3-V1 6.00% Δn 0.1106 CCH-301 3.00% Δε−3.3 CCH-34 9.00% ε_(||) 3.6 CCH-35 8.00% γ₁ 109 mPa s CCP-3-1 8.00%K₃/K₁ 1.12 CCY-3-O2 12.00% CPY-3-O2 4.00% CY-3-O2 8.00% PCH-301 11.50%PY-3-O2 14.50% B(S)-2O-O4 4.00% B(S)-2O-O5 4.00%

The mixture contains two compounds of formula B (B(S)-2O-O4,B(S)-2O-O5), but does not contain a compound of formula Q.

Example 4

The nematic LC host mixture N4 is formulated as follows.

BCH-32 8.50% cl.p. 74.9° C. CC-3-V1 6.00% Δn 0.1106 CCH-301 2.00% Δε−3.3 CCH-34 9.00% ε_(||) 3.7 CCH-35 8.00% γ₁ 111 mPa s CCP-3-1 8.00%K₃/K₁ 1.13 CCY-3-O2 12.00% CPY-3-O2 3.00% CY-3-O2 12.00% PCH-301 10.00%PY-3-O2 13.00% B(S)-2O-O4 4.00% B(S)-2O-O5 4.00% PPGU-3-F 0.50%

The mixture contains two compounds of formula B (B(S)-2O-O4, B(S)-2O-O5)and a compound of formula Q (PPGU-3-F).

Use Examples

Table 1 shows the rotational viscosity of the LC host mixtures C0-C4 andN1-N4 in relation to the concentration of compounds of formula B.

TABLE 1 Rotational Viscosity Host Mixture C0 C1 C2 C3 C4 Conc.B(S)-nO-Om (%) 0 2 4 6 8 Rot. Viscosity γ₁ (mPa s) 117 116 114 112 109Host Mixture N1 N2 N3 N4 Conc. B(S)-nO-Om (%) 2 4 6 8 Rot. Viscosity γ₁(mPa s) 120 114 112 111

From Table 1 it can be seen that, with increasing concentration of thecompound B(S)-nO-Om of formula B, the rotational viscosity of the LChost mixture is decreasing. This shows that the addition of compounds offormula B leads to the advantageous effect of reducing the rotationalviscosity, which results in shorter response times.

Polymerizable Mixtures

Polymerizable mixtures are prepared by adding reactive mesogen M1 toeach of nematic LC host mixtures C0-C4 and N1-N4, respectively, at aconcentration of 0.35 by weight.

The composition of the polymerizable mixtures is shown in Table 2 below.

TABLE 2 Polymerizable Mixture Composition Mix. No. LC Host RM RM conc.(%) CP0 C0 M1 0.35 CP1 C1 M1 0.35 CP2 C2 M1 0.35 CP3 C3 M1 0.35 CP4 C4M1 0.35 P1 N1 M1 0.35 P2 N2 M1 0.35 P3 N3 M1 0.35 P4 N4 M1 0.35

The VHR values of the polymerizable mixtures are measured at 60° C. inVA-VHR test cells before and after UV exposure for 80 min at RT using afluorescent UV lamp type C (305 nm˜355 nm).

The VHR values of the polymerizable mixtures are shown in Table 3.

TABLE 3 VHR values CP0 CP1 CP2 CP3 CP4 VHR at 60° C. (%) VHR/% Initial98.2 98.2 98.4 98.3 98.3 After UV (80 min) 98.1 97.5 96.6 95.2 94.2 P1P2 P3 P4 VHR at 60° C. (%) VHR/% Initial 98.1 97.8 98.1 97.9 After UV(80 min) 97.0 96.7 96.1 95.7

From Table 3 it can be seen that the initial VHR value of allpolymerizable mixtures CP0-CP4 and P1-P4 is approximately at the samelevel.

However, after polymerization the mixtures CP1-CP4 and P1-P4 show, withincreasing amount of compounds of formula B, an increasing VHR drop,compared to the mixture CP0 without a compound of formula B.

On the other hand, in the mixtures P1-P4 according to the presentinvention, which do additionally contain a compound of formula Q, afterpolymerization the increase of the VHR drop with increasing amount ofcompounds of formula B is reduced, compared to mixtures CP1-CP4 which donot contain a compound of formula Q.

This effect is especially significant in the mixtures P2-P4 with higherconcentration of compounds of formula B, where the VHR afterpolymerisation is higher than in the comparative mixtures C2-C4.

Thus, the addition of a compound of formula Q to the LC medium canreduce the VHR drop that is observed when adding increasing amounts of acompound B to the LC medium. The effect is especially significant formixtures with a higher amount of compounds of formula B. Since theaddition of a higher amount of compounds of formula B is desirablebecause it leads to lower viscosity as shown above, the use of mixturesP1-P4 according to the present invention allows to combine theadvantages of both low viscosity and high reliability.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A liquid crystal (LC) medium comprising one or more polymerizablecompounds, one or more compounds of formula B, and one or more compoundsof formula Q

in which the individual radicals, on each occurrence identically ordifferently, and each, independently of one another, have the followingmeaning: R¹, R², R^(Q) are alkyl, alkoxy, oxaalkyl or alkoxyalkyl having1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all ofwhich are optionally fluorinated, X^(Q) is F, Cl, halogenated alkyl oralkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having2 to 6 C atoms, L¹, L² are F or Cl, L^(Q1)-L^(Q6) are H, F or Cl, withat least one of L^(Q1) to L^(Q6) being F or Cl.
 2. The LC mediumaccording to claim 1, comprising a polymerizable component A) comprisingone or more polymerizable compounds, and a liquid-crystalline componentB) comprising one or more mesogenic or liquid-crystalline compounds,wherein component B) comprises one or more compounds of formula B andone or more compounds of formula Q as defined in claim
 1. 3. The LCmedium according to claim 1, wherein the compounds of formula B areselected from the following formula:

wherein alkyl denotes a straight-chain alkyl radical having 1-6 C atoms,and (O) denotes an oxygen atom or a single bond.
 4. The LC mediumaccording to claim 1, wherein the proportion of compounds of formula Bis ≧3%.
 5. The LC medium according to claim 1, wherein the compounds offormula Q are selected from the following formulae:

wherein R^(Q) has the meanings of claim
 1. 6. The LC medium according toclaim 1, wherein the proportion of compounds of formula Q is from 0.05to 2%.
 7. The LC medium according to claim 1, wherein the polymerizablecompounds are selected of formula IR^(a)—B¹—(Z^(b)—B²)_(m)—R^(b)   I in which the individual radicals, oneach occurrence identically or differently, and each, independently ofone another, have the following meaning: R^(a) and R^(b) P, P-Sp-, H, F,Cl, Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN, SF₅ or straight-chain orbranched alkyl having 1 to 25 C atoms, in which, in addition, one ormore non-adjacent CH₂ groups may each be replaced, independently of oneanother, by —C(R⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰⁰)—, —O—, —S—, —CO—, —CO—O—,—O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linkeddirectly to one another, and in which, in addition, one or more H atomsmay be replaced by F, Cl, Br, I, CN, P or P-Sp-, where, if B¹ and/or B²contain a saturated C atom, R^(a) and/or R^(b) may also denote a radicalwhich is spiro-linked to this saturated C atom, wherein at least one ofthe radicals R^(a) and R^(b) denotes or contains a group P or P-Sp-, P apolymerizable group, Sp a spacer group or a single bond, B¹ and B² anaromatic, heteroaromatic, alicyclic or heterocyclic group, preferablyhaving 4 to 25 ring atoms, which may also contain fused rings, and whichis unsubstituted, or mono- or polysubstituted by L, Z^(b) —O—, —S—,—CO—, —CO—O—, —OCO—, —O—CO—O—, —OCH₂—, —CH₂O—, —SCH₂₋, —CH₂S—, —CF₂O—,—OCF₂—, —CF₂S—, —SCF₂—, —(CH₂)_(n1)—, —CF₂CH₂—, —CH₂CF₂—, —(CF₂)_(n1)—,—CH═CH—, —CF═CF—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH—, CR⁰R⁰⁰ or a singlebond, R⁰ and R⁰⁰ H or alkyl having 1 to 12 C atoms, m 0, 1, 2, 3 or 4,n1 1, 2, 3 or 4, L P, P-Sp-, OH, CH₂OH, F, Cl, Br, I, —CN, —NO₂, —NCO,—NCS, —OCN, —SCN, —C(═O)N(R^(x))₂, —C(═O)Y¹, —C(═O)R^(x), —N(R^(x))₂,optionally substituted silyl, optionally substituted aryl having 6 to 20C atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl,alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 Catoms, in which, in addition, one or more H atoms may be replaced by F,Cl, P or P-Sp-, Y¹ halogen, R^(x) P, P-Sp-, H, halogen, straight-chain,branched or cyclic alkyl having 1 to 25 C atoms, in which, in addition,one or more non-adjacent CH₂ groups may be replaced by —O—, —S—, —CO—,—CO—O—, —O—CO—, —O—CO—O— in such a way that O and/or S atoms are notlinked directly to one another, and in which, in addition, one or more Hatoms may be replaced by F, Cl, P or P-Sp-, an optionally substitutedaryl or aryloxy group having 6 to 40 C atoms, or an optionallysubstituted heteroaryl or heteroaryloxy group having 2 to 40 C atoms. 8.The LC medium according to claim 1, wherein the polymerizable compoundsare selected from the following formulae:

in which the individual radicals, on each occurrence identically ordifferently, and each, independently of one another, have the followingmeaning: P¹, P², P³ a vinyloxy, acrylate, methacrylate, fluoroacrylate,chloroacrylate, oxetane or epoxy group, Sp¹, Sp², Sp³ a single bond or aspacer group where, in addition, one or more of the radicals P¹-Sp¹-,P¹-Sp²- and P³-Sp³- may also denote R^(aa), with the proviso that atleast one of the radicals P¹-Sp¹-, P²-Sp² and P³-Sp³- present isdifferent from R^(aa), R^(aa) H, F, Cl, CN or straight-chain or branchedalkyl having 1 to 25 C atoms, in which, in addition, one or morenon-adjacent CH₂ groups may each be replaced, independently of oneanother, by —C(R⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰)—, —O—, —S—, —CO—, —CO—O—,—O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linkeddirectly to one another, and in which, in addition, one or more H atomsmay be replaced by F, Cl, CN or P¹-Sp¹-, particularly preferablystraight-chain or branched, optionally mono- or polyfluorinated alkyl,alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl,alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, where thealkenyl and alkynyl radicals have at least two C atoms and the branchedradicals have at least three C atoms, R⁰, R⁰⁰ H or alkyl having 1 to 12C atoms, R^(y) and R^(z) H, F, CH₃ or CF₃, X¹, X², X³ —CO—O—, —O—CO— ora single bond, Z¹ —O—, —CO—, —C(R^(y)R^(z))— or —CF₂CF₂—, Z², Z³ —CO—O—,—O—CO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂— or —(CH₂)_(n)—, where n is 2, 3or 4, L F, Cl, CN or straight-chain or branched, optionally mono- orpoly-fluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 Catoms, L′, L″ H, F or Cl, r 0, 1,2,3 or 4, s 0, 1, 2 or 3, t 0, 1 or 2,x 0 or
 1. 9. The LC medium according to claim 1, which comprises one ormore compounds selected from the formulae AN and AY:

in which the individual radicals, on each occurrence identically ordifferently, and each, independently of one another, have the followingmeaning:

is

is

is

R^(A1) alkenyl having 2 to 9 C atoms or, if at least one of the rings X,Y and Z denotes cyclohexenyl, also one of the meanings of R^(A2), R^(A2)alkyl having 1 to 12 C atoms, in which, in addition, one or twonon-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—, —OCO— or—COO— in such a way that O atoms are not linked directly to one another,Z^(x) —CH₂CH₂—, —CH═CH—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—, —O—CO—, —C₂F₄—,—CF═CF—, —CH═CH—CH₂O—, or a single bond, preferably a single bond, L¹⁻⁴H, F, Cl, OCF₃, CF₃, CH₃, CH₂F or CHF₂H, x 1 or 2, z 0 or
 1. 10. The LCmedium according to claim 1, which comprises one or more compoundsselected from the formulae CY and PY:

in which the individual radicals have the following meanings: a denotes1 or 2, b denotes 0 or 1,

denotes

R¹ and R² each, independently of one another, denote alkyl having 1 to12 C atoms, where, in addition, one or two non-adjacent CH₂ groups maybe replaced by —O—, —CH═CH—, —CO—, —O—CO— or —CO—O— in such a way that Oatoms are not linked directly to one another, Z^(x) denotes —CH═CH—,—CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —O—, —CH₂—, —CH₂CH₂— or a single bond,L¹⁻⁴ each, independently of one another, denote F, Cl, OCF₃, CF₃, CH₃,CH₂F, CHF₂.
 11. The LC medium according to claim 1, which comprises oneor more compounds selected from formulae ZK and DK:

in which the individual radicals on each occurrence, identically ordifferently, have the following meanings:

denotes

denotes

denotes

and R³ and R⁴ each, independently of one another, denote alkyl having 1to 12 C atoms, in which, in addition, one or two non-adjacent CH₂ groupsmay be replaced by —O—, —CH═CH—, —CO—, —O—CO— or —CO—O— in such a waythat O atoms are not linked directly to one another, Z^(y) denotes—CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —COO—, —OCO—, —C₂F₄—,—CF═CF— or a single bond, R⁵ and R⁶ each, independently of one another,denote alkyl having 1 to 12 C atoms, where, in addition, one or twonon-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—, —OCO— or—COO— in such a way that O atoms are not linked directly to one another,preferably alkyl or alkoxy having 1 to 6 C atoms, e denotes 1 or
 2. 12.The LC medium according claim 1, wherein the polymerizable compounds arepolymerised.
 13. An LC display comprising an LC medium as defined inclaim
 1. 14. The LC display of claim 13, which is a PSA type display.15. The LC display of claim 14, which is a PS-VA, PS-IPS or PS-UB-FFSdisplay.
 16. The LC display of claim 14, characterized in that itcomprises two substrates, at least one which is transparent to light, anelectrode provided on each substrate or two electrodes provided on onlyone of the substrates, and located between the substrates a layer of anLC medium comprising one or more polymerizable compounds, one or morecompounds of formula B, and one or more compounds of formula Q

in which the individual radicals, on each occurrence identically ordifferently, and each, independently of one another, have the followingmeaning: R¹, R², R^(Q) are alkyl, alkoxy, oxaalkyl or alkoxyalkyl having1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all ofwhich are optionally fluorinated, X^(Q) is F, Cl, halogenated alkyl oralkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having2 to 6 C atoms, L¹, L² are F or Cl, L^(Q1)-L^(Q6) are H, F or Cl, withat least one of L^(Q1) to L^(Q6) being F or Cl. wherein thepolymerizable compounds are polymerized between the substrates of thedisplay.
 17. A process for the production of an LC display according toclaim 16, comprising the steps of providing an LC medium between thesubstrates of the display, and polymerising the polymerizable compoundstherein, wherein the liquid crystal (LC) medium comprises one or morepolymerizable compounds, one or more compounds of formula B, and one ormore compounds of formula Q

in which the individual radicals, on each occurrence identically ordifferently, and each, independently of one another, have the followingmeaning: R¹, R², R^(Q) are alkyl, alkoxy, oxaalkyl or alkoxyalkyl having1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all ofwhich are optionally fluorinated, X^(Q) is F, Cl, halogenated alkyl oralkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having2 to 6 C atoms, L¹, L² are F or Cl, L^(Q1)-L^(Q6) are H, F or Cl, withat least one of L^(Q1) to L^(Q6) being F or Cl.
 18. A process ofpreparing an LC medium according to claim 1, comprising the steps ofmixing one or more compounds of formula B defined below with one or morecompounds of formula Q defined below and one or more polymerizablecompounds of formula I defined below, and optionally with further LCcompounds and/or additives,

in which the individual radicals, on each occurrence identically ordifferently, and each, independently of one another, have the followingmeaning: R¹, R², R^(Q) are alkyl, alkoxy, oxaalkyl or alkoxyalkyl having1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all ofwhich are optionally fluorinated, X^(Q) is F, Cl, halogenated alkyl oralkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having2 to 6 C atoms, L¹, L² are F or Cl, L^(Q1)-L^(Q6) are H, F or Cl, withat least one of L^(Q1) to L^(Q6) being F or Cl;R^(a)—B¹—(Z^(b)—B²)_(m)—R^(b)   I R^(a) and R^(b) P, P-Sp-, H, F, Cl,Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN, SF₅ or straight-chain orbranched alkyl having 1 to 25 C atoms, in which, in addition, one ormore non-adjacent CH₂ groups may each be replaced, independently of oneanother, by —C(R⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰⁰)—, —O—, —S—, —CO—, —CO—O—,—O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linkeddirectly to one another, and in which, in addition, one or more H atomsmay be replaced by F, Cl, Br, I, CN, P or P-Sp-, where, if B¹ and/or B²contain a saturated C atom, R^(a) and/or R^(b) may also denote a radicalwhich is spiro-linked to this saturated C atom, wherein at least one ofthe radicals R^(a) and R^(b) denotes or contains a group P or P-Sp-, P apolymerizable group, Sp a spacer group or a single bond, B¹ and B² anaromatic, heteroaromatic, alicyclic or heterocyclic group, preferablyhaving 4 to 25 ring atoms, which may also contain fused rings, and whichis unsubstituted, or mono- or polysubstituted by L, Z^(b) —O—, —S—,—CO—, —CO—O—, —OCO—, —O—CO—O—, —OCH₂—, —CH₂O—, —SCH₂₋, —CH₂S—, —CF₂O—,—OCF₂—, —CF₂S—, —SCF₂—, —(CH₂)_(n1)—, —CF₂CH₂—, —CH₂CF₂—, —(CF₂)_(n1)—,—CH═CH—, —CF═CF—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH—, CR⁰R⁰⁰ or a singlebond, R⁰ and R⁰⁰ H or alkyl having 1 to 12 C atoms, m 0, 1, 2, 3 or 4,n1 1, 2, 3 or 4, L P, P-Sp-, OH, CH₂OH, F, Cl, Br, I, —CN, —NO₂, —NCO,—NCS, —OCN, —SCN, —C(═O)N(R^(x))₂, —C(═O)Y¹, —C(═O)R^(x), —N(R^(x))₂,optionally substituted silyl, optionally substituted aryl having 6 to 20C atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl,alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 Catoms, in which, in addition, one or more H atoms may be replaced by F,Cl, P or P-Sp-, Y¹ halogen, R^(x) P, P-Sp-, H, halogen, straight-chain,branched or cyclic alkyl having 1 to 25 C atoms, in which, in addition,one or more non-adjacent CH₂ groups may be replaced by —O—, —S—, —CO—,—CO—O—, —O—CO—, —O—CO—O— in such a way that O and/or S atoms are notlinked directly to one another, and in which, in addition, one or more Hatoms may be replaced by F, Cl, P or P-Sp-, an optionally substitutedaryl or aryloxy group having 6 to 40 C atoms, or an optionallysubstituted heteroaryl or heteroaryloxy group having 2 to 40 C atoms.